Most casinos are strict on the number of accounts that a single player can have. Unless stated otherwise in the terms and conditions, you can only have one account, and you will use the same details to access the casino mobile site.
However, you can sing up at as many casinos as you wish, and you won’t have any problem using their services. But you risk being banned from playing if you try to use the same details to sign up for a separate account to play on the mobile casino app.