Chapter 5

1. Yes, but it is not recommended. You will have to then explicitly specify the names of both roles.
2. Yes. This is managed by a property called Maximum Concurrent Accounts.
3. Per AWS Region (as they are defined from the first to last) and then per account (as they are defined from the first to last).
4. No. You must delete all the stack instances first.
5. The only action for the Administrator role is to assume the Execution role.