1.OK, I need to do th normal instant withdrawal for members of my site like say when using PM, Payeer, Okpay etc, which API can I use for this.
Again ,I don't get the point.You're looking for bitcoin withdrawals or other commercial services withdrawal ? If you have to implement PM/PayPal API ,you can simply visit their sites and see the API section.I'm sure they have the code,you just have to send RPC to them.
1. I need a bitcoin instant payment system that can do instant withdrawal for my members of my new site, is there such an API for Bitcoin instant withdrawal?
That makes sense,there are a lot of API's just to send/receive money.Further it depends what else you wish to do?
-Provide last transactions for x user ?
-Fetch last transactions ?
-Show balances ?
Depending on your choices you'd choose a suitable API.I have linked a few simple one's below.
https://blockchain.info/apihttps://developers.xapo.com/The Hard Way :
https://en.bitcoin.it/wiki/Original_Bitcoin_client/API_calls_list