Membership Plugin Questions 2

Hello and thank you for the quick answers to my previous questions.

I have a couple more questions,,,

1. If I select Standard mode in setting up my membership site, can I later change to Advanced mode?

2. How can I give a guest membership that will automatically expire in 3 days?

3. If I have multiple levels of subscription... and a person wants to upgrade... how are the charges handled? Are they charged a pro-rated amount for the time left in their current subscription? Thereafter, charged the correct amount for the level to which they upgraded?

4. If a visitor tried to join... but they fail (maybe credit card isn't valid or something like that)... are they still registered as a user, but not a member?
I ask this question because another membership plugin did that and I found it very annoying.
I would prefer that a failed attempt at joining puts no record in the user db and no record in the membership db. Is that possible?

Thank you,

Jerry Perrich