How to recover the database with old data?
if you have a base backup AND full WAL archives you can use point in time recovery.  Otherwise you are stuck.  good luck.  I hope you have something you can work with.

Otherwise you are screwed.  There is no way to roll back restoring a backup in this way.  If you didn't drop relations in the process you MIGHT be able to sort things out using min_xid columns on the tables.  In that case you will have a lot of work.....