SBS 2003 R2 - Server 2008 R2

On the internet i read alot about the 21 days grace period after migration of the FSMO roles.

Is the grace period only when i add a SBS 2008/SBS2011 server to the domain or also when i add a non SBS server?

Does the 21 days grace period start after i added the domain controller?
Does the 21 days grace period only start when i migrate the FSMO roles?
Can i add 2 Domain Controller or do i first have to migrate all to 1 domain controller?
Can i see if the grace period has been started?
Can i view somewhere how many days are left?

Thanks all!