Upgrade from 1.2 to 1.6, external DB, mysql errors

Can anyone tell me if I need to do a step upgrade from 1.2 to 1.6 using intermediate versions? I have seen a couple posts asking somewhat similar questions but without a clear answer.

My situation is attempting upgrade from 1.2 to 1.6 and the new 1.6 server fails to start (continually restarts, actually). I am using an external mysql server (was working successfully on 1.2) and the log errors are showing db migration errors: mariadb error 150, specifically “Can’t create table” for what appears to be temp tables used during the upgrade.

The db user has needed permissions to create tables (same user/permissions were used while on 1.2 with external DB as well).