Good luck. As stated do ensure you got a proper full current backup.
Last thing you want is an irreversible error. Once the DB Schema has been updated, removing a patch will not revert that process.
Hence backups of at least the Databases are critical (includes master db etc)
You can deploy only SP2 (first link) but best practice is to deploy the lot. They compliment and improve upon each-other.
Cumulative Update is highly recommended. These are released once every quarter from memory and not always available through Windows Update prior to SQL 2016.