With direct payment turned on, if there are multiple memberships setup, then a drop down appears for the person to select which membership to join. This controls if the membership appears in that drop down.
When editing the membership, in the URL at top you can see the id for the membership. Then, use that id for the membership and add it to the url as shown below replacing the id number with ID:/join/USERNAME?membership=ID
So, for example if it is for username john and membership id 3 it would look like:/join/john?membership=3
Or if putting it inside the WYSIWYG of a capture page you would put the following code for membership id 3/join/~username~?membership=3
A member is suspended when their payment is canceled. Our software is notified by an IPN when a subscription is canceled and the member is suspended immediately. There is a setting that can be turned on to have them suspended when their next payment would have been due, but by default this is turned off, and this should be used carefully because it will suspend anyone that doesn't have a payment record.
If an existing Member purchased into a separate membership if they use the same email, then they would cancel their old subscription and would belong to the new membership. If they use a new email and have 2 separate accounts, then they would have 2 separate logins and see separate things in each members area.