1) When you install the JMS patches, it restores the latest Joomla installation directory to allow creating new fresh slave sites.
2) If you simply replicate a website, this copy everything including the users (login, email, ...)
If you propose the website creation from the front-end, see tutorial video 13
www.jms2win.com/tutorial#jms12x-13
In this case, you can define in the JMS template which login is "public' and for which the user can change the email and password.
3) YES you can continue working with PHPMyAdmin as usual.
JMS does not modify the table columns or things like that.
Only when you decide to share MySQL table, it creates them using a view on the original one.
You can continue create backup as usual.
When you have independent website and decide to continue using separated DB, nothing is changed.
Personnally, I am using PHPMyAdmin export / import for the backup / restore.
YES you can decide to have several domain for a slave site.
You can define in JMS that you have
-
www.mysite.com/theirsite/
synonym of
-
www.theirsite.com
or
- theirsite.com (without the WWW).
This is free.