Failover replication with different SQL versions

HI,

We are planning to implement a failover replication site for SEPM version 12.1.4104.4130. Currently there are two servers in primary site with SQL 2008 R2 . Both are configured with priority 1. There are more than 600 branch offices which use GUP  for antivirus updates. Now we are planning to configure a remote site with SQL 2012 , with priority 2. Live update in primary site is happening once in 4 hours. The database in primary site is more than 40 GB. 

1. What are the necessary checks that need to be done before configuring replication ?

2. Do we need to turn off Live update before starting the initial replication ?

Please help.

Thanks and regards,

Bijumon.C