I will include a few quotes from this SEP entry, but this would be a great SEP entry for you to read through as it pertains pretty directly to your question. I just read the whole thing just for this answer haha, and it was very interesting. https://plato.stanford.edu/entries/lying-definition/.
So regarding honesty vs "truth telling". They are at least in a certain sense unrelated. Honesty is the attempt to tell the truth, it is telling what you believe to be true. For example, I could tell you "2+2=4", and I would be being honest. Not because it's true, but because I believe that it's true. This is an example where I was both honest and told the truth. To illustrate that here's a different example. Let's say hypothetically that I believe the earth is flat. Then I could tell you "The earth is flat", and that would also be honest even though it's not true. It's honest because I told you what I believed to be true.
"According to the untruthfulness condition, lying requires that a person
make an untruthful statement, that is, make a statement that she
believes to be false. Note that this condition is to be distinguished
from the putative necessary condition for lying that the statement that
the person makes be false (Grotius 2005, 1209; Krishna 1961, 146). The
falsity condition is not a necessary condition for lying according to
L1." (SEP, from link above)
Honesty is simply speaking/writing (or whatever mode of communication) in a way that accurately conveys your beliefs, not necessarily the truth. Again it can be true, as in my first example, but truth is by no means a necessary condition for honesty.
"Truth telling", of course also has no necessary connection with honesty. For example, imagine you are asking me for help with basic trigonometry. Unfortunately, unbeknownst to you I despise you, so I decide to give you the wrong answer. So I tell you this: "The tangent of an angle is equal to the length of the opposite side divided by the length of the adjacent side." Fortunately for you I'm really not that good at math, so I actually believed that the sine of an angle had that formula instead of tangent, and I was actually trying to deceive you so that you would do worse on your next math test. In that situation I told the truth, as I'm sure you know (after all tan(theta)=opposite/adjacent is indeed the correct formula). But at the same time I was not honest. I attempted to lie to you, since I believed that the formula I gave you was wrong(even though in actuality it is correct). "Truth telling" is simply whether or not you tell someone what is objectively true.
And of course telling the truth and honesty can go together as well. For example if you asked me "Have you ever broken a bone?" I could say "Nope, I've never broken a bone." I believe that it's true, so I am indeed being honest, and it also happens that it actually is true(I have never broken a bone), so I'm also telling you the truth.
So to address your last question, I'll give a couple well known philosophical perspectives. Kant would say(well there are many different interpretations, but I believe this is the most well known and accepted as being what Kant intended) that lying is always wrong. This comes from his Categorical Imperative which has multiple forms, although Kant claims they are all equivalent (https://plato.stanford.edu/entries/kant-moral/#DutResForMorLaw) so I will pick the Universal Law. "act only in accordance with that maxim through which you can at the same time will that it become a universal law" (SEP, link from like 2 lines up). That SEP entry gives an example in which, if you decided to lie to steal money, according to Kant for that to be moral you would have to wish that every single person would also make the decision to lie to steal money. But if everyone did that, then society would break down because no one would be able to trust each other. I believe he is completely literal when saying that lying is never ok, no matter what. (Sorry can't find a source, but I've read it quite a few times.)
I disagree, so here is a consequentialist/utilitarian argument and example. To way way oversimplify, consequentialism/utilitarianism focus on the overall welfare (or utility) of either society as a whole, or just locally who is affected by whatever decision you're making. Both my grandparents have been very sick. About two weeks ago, my grandpa died, and my grandma is completely bedridden(literally has a hospital bed in her room), and her memory is completely gone. She forgets everything within a few seconds, or a minute or two at most. She usually asks me what college I'm attending about 30 times a conversation. (I'm just emphasizing how truly non existent her memory capacity is because it's important). The first time I talked to her after my grandpa's funeral, she asked me where he was probably about 15 times. I told her each time that he was dead. She was going through the immense, horrible pain of learning that her husband died for the first time every single time I told her. It was obvious it hurt so so badly, it was truly the first time she had heard it (in her mind) every single time. I eventually realized that she's completely bedridden, not even in charge of her own property anymore, the funeral and everything was taken care of by her family members since she isn't really able to do things anymore, and simply has no important (or even trivial) decisions she can make. In other words, there was literally absolutely no good that could come from telling her the truth because there will never be a decision she makes where she needs to know, and because she can't even go to therapy and come to terms with what happened, because her memory would never let her remember. If everyone in my family told her the truth, she would be subjected to finding out for the very first time that her husband had died, over and over and over again, every 5-10 minutes for the rest of her life(except when she's sleeping). To me, wishing that on anyone is unacceptable, and any ethical system that would allow that must be flawed.
My approach about the situation in the above paragraph was a utilitarian approach. I simply chose the option that (as best as I could tell) would maximise pleasure (or utility/happiness, whatever term you want), or at least minimize suffering, and that option just happened to be to lie. I should point out that there is a definition of lying that actually would exclude the knowing, intentionally deceptive untruths I said to my grandma to not be considered lying. The following definition of lying, and brief follow up is from my first link to SEP in the first paragraph.
(L11) To lie =df to freely make a believed-false statement to another
fully responsible and rational person, with the intention that that
other person believe that statement to be true [or the intention that
that other person believe that that statement is believed to be true, or
both]. (Donagan 1977)
According to L11, it is not possible to lie to “children, madmen, or
those whose minds have been impaired by age or illness” (Donagan 1977,
89), since they are not fully responsible and rational persons. It is
also not possible to lie to “a would-be murderer who threatens your life
if you will not tell him where his quarry has gone” (Donagan 1977, 89),
and in general when you are acting under duress in any way (such as a
witness in fear of his life on the witness stand, or a victim being
robbed by a thief), since statements made in such circumstances are not
To me this seems more like an attempt to assign inherent wrongness to lying than to produce a coherent definition though. Additionally, this definition seems to be very confused about free will, conflating a true lack of free will with simply acting a certain way out of fear. A person being robbed at gunpoint (temporarily just assuming free will exists for sake of argument) has no less free will than any other person has ever had. They would still be free to choose defying the assailant, it would just be a hard choice to make since they know that they are essentially choosing death. Nevertheless, the decision that person makes is free in terms of actual free will, just as much as someone choosing to get ice cream or cake. So I don't think that is a great definition. I'll just conclude with a (albeit rare) piece of still applicable wisdom about Kant that I think answers you most directly.
The philosopher Immanuel Kant said that lying was always morally wrong.
He argued that all persons are born with an "intrinsic worth" that he
called human dignity. This dignity derives from the fact that humans are
uniquely rational agents, capable of freely making their own decisions,
setting their own goals, and guiding their conduct by reason. To be
human, said Kant, is to have the rational power of free choice; to be
ethical, he continued, is to respect that power in oneself and others.
Lies are morally wrong, then, for two reasons. First, lying corrupts the
most important quality of my being human: my ability to make free,
rational choices. Each lie I tell contradicts the part of me that gives
me moral worth. Second, my lies rob others of their freedom to choose
rationally. When my lie leads people to decide other than they would had
they known the truth, I have harmed their human dignity and autonomy.
Kant believed that to value ourselves and others as ends instead of
means, we have perfect duties (i.e., no exceptions) to avoid damaging,
interfering with, or misusing the ability to make free decisions; in
other words - no lying. (https://www.scu.edu/ethics/ethics-resources/ethical-decision-making/lying/)
Lying is usually wrong, because it is treating people as a means, rather than an end in themselves. It is disrespecting their autonomy, and you are robbing them of the ability to make as informed of a decision as they could have if you told the truth. I think this is a great point, and I totally agree with it, I just think he takes it too far saying that you can never lie. That's why I like the consequentialist perspective better. If people followed consequentialism, it would still lead people to not lie the vast majority of the time, but it will also tell people that they should lie when for example it might save a life, or save someone from enormous suffering.