What would happen if I dont like XT or XT crash, may I come back to BTC?
Yes, if you did not touch the BTC chain after the fork. If your Bitcoin was only transacted on the XT fork, then if you decide to use the old BTC chain, you will have however many BTC you had prior to the fork.
This is not true, and anyone who follows this advice will lose their funds for sure. Unless you go out of your way to double-spend your pre-fork coins so that they end up in different outputs on each chain, it is very likely that any transaction you make on one chain will be mirrored on the other. Since the ledger and the unconfirmed transaction pool are public, anyone can copy your transactions and broadcast them on the competing chain. If you plan to keep funds on the real chain as a backup for your XT derpitude, you should better split them first so that it is impossible for others to mirror your transactions in the future.