Need to add EDGE 2010 to Exchange 2013 Organization

I have a Exchange 2007 Organization and I am planning to Migrate to Exchange 2013 with one CAS and one Mailbox servers. I also want to have a Exchange 2010 EDGE server for Exchange 2013 servers. 1. What is the sequence of installing the servers including 2010 EDGE. 2. Should I do Exchange 2010 Schema update before doing Exchange 2013 Schema update since I am deploying Exchange 2010 as EDGE (I understand it wont be part of AD but want to know if EDGE sync will be affected if I dont do Exchange 2010 Schema update) .