E-Commerce Question (Kinda)

I have a customer who has asked me to create her a language games site for her language students.

I have set up the game she wanted (crossword via CrossWord Forge) on a basic wordpress theme, but she wants to limit demo access to say 3 crosswords for example and require people to subscribe/pay for extended/unlimited access.

What is the best way to do this?

I’m guessing PayPal and WordPress accounts, so a potential customer clicks ‘Pay’ via a PayPal button, then once Payment has been confirmed, a WordPress account with access to the extended games is created, with the login credentials emailed to them.

So I have a few questions;

1: Can I limit the game access via different tiered wordpress accounts?
2: Can I automate the process of account creation upon payment?
3: How would you go about this process?

Thanks in advance for any suggestions