"Change" last forever? If not what fallacy breaks the chain of reasoning shown here?

Question

In movies, a frequently mentioned idea is that "Nothing lasts forever" .There's also a Chinese saying 變幻是永恆

Having thought too much into treating concepts as something similar to "building blocks", I end up having the following reasoning that contradicts itself:

1. Nothing lasts forever without changing
2. Everything Change or last for a finite time or both

(Elaboration)

3. Therefore, there is Change that last forever without changing

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Elaboration (because I have no idea how to simplify it into sentence form...):

Things change when it no longer possess the nature or qualities it originally had. For example "an apple falling from the tree" is an example of change, because at least one of its qualities, its position, is no longer fixed in at least one reference frame.

Therefore anything that differs from what it originally is has changed

So when a quality x of a given thing started to deviate, say to x1, it has changed

Put it another way, it has acquired the quality "changed"

Since this quality cannot be removed by any means (you cannot "unchange" something because restoring it to what it is originally should be, is just x1 becoming x, thus still "changed". Even if time travel where overwriting history is possible, then the quality still goes from x1 back to x in the perspective to the person who read the time travelling story)

so it does sounds like, once the quality "changed" is acquired, it will last for indefinite period of time, and because of the stuff mentioned above, "changed" cannot change

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However since 3 contradicts 1, I suspect it is because of one or more of the following:

1. There is a logical fallacy
2. Change cannot be considered as a quality
3. It is possible to unchange something
4. The definition of change as "Things change when it no longer possess the nature or qualities it originally had" is worng or misused or incomplete etc.

So my question the becomes:

1. what is my logical fallacy, hidden assumption or missing information, if any?

2. If change is not a quality, then what kind of concept is it?

3. How to demonstrate/illustrate the "unchange" of something, if it is possible?

4. How to better define the concept "change" that might help resolve the contradiction?

Answer 1

1. what is my logical fallacy, hidden assumption or missing information, if any?

Buddhism teaches that impermanence (analogous to "change") is a characteristic of any/all "component things" or "compound things" i.e. of things which have been put together: which are also called "conditioned phenomena" because their existence depends on or is conditioned by other things.

Among "impermanent phenomena" are Saṅkhāra: which includes things imagined and things desired.

But impermanence/change itself is not a "compound thing".

2. If change is not a quality, then what kind of concept is it?

It's a characteristic of things, not a thing.

Things are impermanent.

Impermanence is not necessarily impermanent (because impermanence is not a thing).

3. How to demonstrate/illustrate the "unchange" of something, if it is possible?

There's a well-known expression, "you can't step into the same river twice." (perhaps attributed to Heraclitus).

You may be introducing an extra confusion when you say that "a thing has changed", or that "some specific change is a permanent property of some thing": because in reality the changed thing isn't the same thing as the previous thing (see the Ship of Theseus).