MySQL percona 5.6 to MySQL 5.5 replication
It isn't clear what you're asking in scenario 1.

As for scenario 2, you can have a slave that's a higher version than the master, but not vice-versa. From the documentation:


  MySQL supports replication from one release series to the next higher release series. For example, you can replicate from a master running MySQL 5.5 to a slave running MySQL 5.6, from a master running MySQL 5.6 to a slave running MySQL 5.7, and so on.