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.
This is my impression too. If Alice sends Bob 1 XBTC on the XT-network, Bob can publish the same transaction on the BTC-network and get Alice's 1 BTC too. I assume this will happen if both chains survive. The way to get around this is either easy (don't spend anything) or takes a little work:
Alice could send her 1 XBTC to her address A on the XT-network and her other address B on the BTC-network. At that point the two coins can be spent independently. It might take several tries to do this successfully, since when she spends 1 XBTC to her address A someone might publish the same transaction on the BTC-network before she can send the 1 BTC to address B. If that happens, try again until it doesn't. The point is: don't pay anyone other than yourself until the two coins are separated.
Should be a lot of fun to watch. I guess it's a good reason for people to learn a little more about how Bitcoin actually works.