Can a member upgrade their membership in Protected Content?

Hi, I really need an answer to this, but so far haven't had an answer that relates to my question, so I am reposing in the hope there is someone who understands

I have set up a Protected Content Membership Site where 12 weeks worth of content is drop fed for 12 weeks. There are 3 levels of membership (monthly, quarterly and annual) which are collected by recurring payments.

At the end of the 12 weeks, there is more content, which of course due to the set up of recurring payments, will still be accessible to members, so my questions are:

1. If a member wants to switch their membership from monthly to quarterly or annually, is this possible? If so, how?

2. If I want to change my membership set up to tiered memberships? I did the wizard to set up drip feed content, but can't find a way to change this back to the original set up.

3. If I do find a way top set up tiered memberships, can I also drip feed content? If so, how.

Pleeeeeaaaaase help!

Thanks.