SQL Server Standard 2016 Service Pack and Cumulative Update

We are currently using SQL Server 2016 Standard Edition with ALWAYS-ON High Availability. We have two different clusters of SQL servers. We need to update it to the latest version of SQL (As per my research Cumulative Update package 13 (CU13) for SQL Server 2016 SP) Cluster 1 - Currently on Microsoft SQL Server 2016 (SP2-CU4) (KB4464106) - 13.0.5233.0 (X64) Cluster 2 - Currently on Microsoft SQL Server 2016 (SP1-CU12) (KB4464343) - 13.0.4541.0 (X64) Query 1 - Can we update SP1-CU12 to directly SP2-CU13 Query 2 - Can we update SP2-CU4 to directly SP2-CU13 Query 3 - What steps should be taken before and after upgrading Query 4 - What should be the roll-back plan, incase of failure Any other word of advice or caution for someone doing for the first time will be appreciated.