Your question contains some confusion. There are several different accounts of how to understand or use 'probability'. The most common are:
- Classical - that probabilities are understandable in terms of some real or hypothetical symmetry.
- Frequentist - that probabilities represent some long-run frequency of a series of events.
- Logical - that probabilities are a partial degree of entailment of a proposition by other propositions.
- Subjective - that probabilities are a degree of belief or degree of uncertainty in a proposition on the part of a real or ideal reasoning agent.
- Propensity - that probabilities arise from physical dispositional properties.
What makes them different is that they represent fundamentally different quantities.
In the case of rolling a real die, there is no guarantee that the probability of it landing on a six is 1/6. The die is only symmetrical within some specific engineering tolerance when it was made. If it has been rolled a lot before, its edges may become worn unevenly. The action of rolling it may not yield a perfectly uniform distribution of outcomes. The die may come to rest on an edge or a corner. (Coins when tossed come to rest on their edge more often than you might think.) The probability of the die exploding is very low, since we are aware that such events are extremely rare.
Commonly when we speak of the probability that a die will land six when it is next rolled, we are speaking of the appropriate degree of uncertainty that attaches to this proposition, given all the available evidence. In the absence of any evidence of bias, an assessment of approximately 1/6 is reasonable. On the other hand, if the die has already been rolled and landed six, and we can see that it is six, then updating our belief with this information yields a probability of 1, since we are now certain.