Of course not. Religion is a choice if one becomes religious as an adult. However, for the vast majority of religious people, they become religious at a young age, when they cannot make any choices.

You certainly have the choice whether to continue being religious as an adult. Also, there are plenty of children who reject religiosity (although that may not get a chance to express itself until high school / college)

Not provable to others. Many people are religious on the basis of religious experiences experiences, some on philosophical or other arguments that others find unconvincing. some even do not want to believe - CS Lewis described himself as 'the most dejected convert in England' for this reason.

I don't think it's a choice. If you don't believe something, no amount of trying to make yourself believe it is going to make it so. A whole lot of people raised in a religion who are now atheists can attest to the extreme mental turmoil trying to do so during the deconversion process can cause. You either believe, or don't believe in any given brand of supernatural unobservable phenomenon.

I wouldn't want to assume the details or the difficulty someone else has or is going through related to this.

What I have found helpful, when I went through something like this, is to distinguish between the "feeling" of certainty and the "choice" to put my faith in something. A lot of the time, we talk about "faith" and we conflate those two. I can choose to trust something and not feel confidence in it until after the fact. How much confidence I feel in a choice varies for a lot of reasons, but I may still choose to accept the risk and act on the little information I do have because I don't have better alternatives.

In that sense, you can choose what you believe. Or at least, you can choose what you put your faith in.