What do you mean by expiration date?
As long as you follow TOS, You will have hosting account and you will have this domain associated to your account.
The database username should be like yourCpanelUsername_DatabaseUsername
Database name should also look like YourCpanelUsername_DatabaseName
check here --> MySQL
Yes, you can check How to Use Your Own Domain
By the way, I unsuspended your account, It was suspended for inactivity, You have to login to forums atleast every 30 days to avoid inactivity suspension.