Would it be generated on every IP login, will a single IP get multiple addresses to pay to when they access the forum as guests. I don't know how much data the forum stores, but for this to happen I guess it'll need to access every unique login and know when the forum is accessed from a new device.

This is going to be complicated to implement, the captcha bypass works fine for now and if you click on always logged in you will not need to go through it once logged in.

It's not a paid option, it is available when logging into your account, so to access it, you'll need to log out and click on it to get your unique log in link.