1. Does this apply also if I'm moving from 2008R2 to 2012?
Yes, it will work as it's Microsoft functionality.
2. Would it also work if the SQL Server 2008R2 and the 2012 have different IP addresses?
backup and restore does not depend on IP address, however when you run SEPM configuration wizard you have to enter the IP address of the new SQL server so that it will synch with the database.