People will just lie. If you want to make it restricted, require them to sign a message from an address with BTC in it. You could automate this. Present them a unique message tied to their account they need to sign from an address with say >= 1 BTC or something. They could paste in the signed message along with their address and your system could verify it came from the address they claimed, as well as check the balance of that address. This filters out both users who don't know how to sign messages, and users without any BTC.
thank you for your reply , there is no point to make it restricted !? we only think about the level of users , VIP ... they will have some benefits , we will update this too , we are adding what users need , thank you again