1. when u open wallet on blockchain, u need enter "Identifier", the "Identifier" is not the address which u send & receive BTC, is it?
Nope The Identifier is not your Wallet Address
Does the "Identifier" only use on blockchain wallet or it can also use on other wallet?
The Identifier is specific to Blockchain.info Wallets.
3. If the "Identifier" is only use on blockchain wallet, if I create a new account on other wallet web site, How can I use the same address of send & receive BTC? Or it is not compatible with each other？
The new site would give you a seperate wallet address from that wallet you can send to other wallet addresses. (Your identifier is not used as an address to send anything to. It is just part of the login credentials from blockchain.info)
Hope that it helps! If you want to learn more you can always check out the BitCoin University.
http://www.btccollectorsclub.com/admin]]http://www.btccollectorsclub.com/admin
