This is a forum where people can be quite direct, and open. Unless you are rude, propagating child abuse, or similar things, a lot is tolerated here. We are also used to people asking questions that were asked before: there are way too many topics and posts nowadays to expect someone to read and remember them all. And if you do say something that is not appreciated, most people will let you know relatively kindly. So please don't worry and feel free to express yourself.
It is probably wise to be somewhat careful with personal data though: make sure you don't post enough details that people might figure out who you are, and since most topics can also be read by non-members, be careful with sharing too intimate details. If you are asked about something you don't feel comfortable sharing, just say so or ignore the question. Sometimes we get over-enthusiastic with asking details to be able to give you the best advice, or just plain curious.
kat_anders i think the bra is to much, the bands maybe i dont know
Let me say first that I strongly disapprove of any chastity devices on minors where it is the parents who want that (most), and even if a minor reluctantly agrees it is at least close to child abuse. I can see about your older sister that your parents could be quite scared that that would happen to you as well, but wearing a belt only at the times when that might happen, so mostly when you go out, would be sufficient for that. To totally block any touching also seems unfair compared to your sister, at the very least. But it is hard to argue with religious beliefs.
Are you planning to fight your parents on the bra and thighbands, or even refuse to wear them? Both make your life quite a bit harder (bands physically, bra emotionally), so if you don't see their use, you should at least speak up against them. And especially the thighbands don't add much security: the belt itself already protects 100% against sex, and close to 100% from directly touching your most sensitive area's. For what I have read, thighbands protect a little extra against some stimulation (not enough), perhaps at getting something small under the belt to stimulate, and they make fighting the belt so hopeless that a fight often lasts shorter. All very minor benefits compared to all the extra trouble they give.
If your parents are adamant that you should not be able to touch your breasts, I can't deny that a bra is effective against that, but even with all the people here that are already put in chastity belts, very few of the parents find touching breasts so bad that they decide to lock those away from their children too. (even though it seems to me more than a few years ago)