Email custom URL to validate registation

I have a few questions regarding the security assist registration.

#1 The pre-build solution for Registration and login is exactly what we need. Specifically the feature where a custom URL is sent to the registrant's email address which they need to click on in order to validate their registation.

Is this feature NOT in Security Assist already?
If so where?

#2 Is it possible to have the username = email address, and password is variable. However when the user logs in, we are able to assign the uniqueid as the username, as opposed to the email address?

#3 Does SA use any server side security measures besides form validation and encryption?

Need to decide if purchasing the pre-built solution makes sense, since we already own all the tools that are necessary to create it?

I'm glad to see that this forum is very active.

Thanks in advance for your help.