It depends on the payment processor as some payment processors will retry the credit card on another date. Once the payment processor stops retrying the card and the membership is cancelled in their system they send a notification to our software which suspends their account as if they had canceled.
Under "Advanced Features
there is an option for 'Software is FREE' where you can select no,
making it where someone has to pay before creating their account.
A member cannot belong to more than 1 membership. Instead, you can setup so each membership has different content.
Then make the membership that the member upgrades to include all the content from the member's original membership.
You can do this by setting up content groups and attaching them to content.
You can modify new downline notification, new commission notification without any issues. You should not turn test payments on except if you are doing a test payment. While test payments are on real payments will not work and vice versa.