OP, I am sure you have the best intentions in mind but I hope you can see for the comments that what you are trying to do is a bad idea. You will never get it p

OP, I am sure you have the best intentions in mind but I hope you can see for the comments that what you are trying to do is a bad idea. You will never get it perfect, you will lose a ton of business for no reason (for example: because the customer was an Apple user, guess what: most paying customers are) and you will gain a false sense of security that you are preventing malicious traffic. Just focus on bot detection and tried methods such as credit card or cellphone verification.