relating back up and recovery

Is this a homework or certification question? Please forgive me if it is not, but it sounds a lot like a question from the MCTS.

Anyway, the first question is do you have log backups and is it in full recovery mode? If so, attempt to do a backup of the remaining log tail, then restore the full, restore the 8:00PM differential, and then restore the log backups.

If not, restore the full and the 8:00pm differential and accept that you have lost all changes from 8:00 - 9:00. Then seriously consider if you can afford that kind of data loss and consider if you need to implement log backups.

A differential backup includes everything since the last Full backup (that didn't use the COPY_ONLY option). Therefore, any restore sequence will only require at most one differential backup.

You Can bring your database online till 9 PM if it is is Full Recovery Mode and Apart of this Policy you must also take the log backup.

if you have the Transaction Log back then only you can bring the Server Online. in this scenario you can come up 8 PM.