According to your description, if you want to uninstall SQL Server 2012 SP1 completely, you need to note that the service pack makes changes to the system tables for maintenance reasons, and upgrades
user and distribution databases that are members of a replication topology. Due to these changes, you cannot easily remove service packs. There is no automated way to remove a service pack, and the process of removing a service pack involves several manual
steps and risks if not done correctly.
There are more details about how to remove a SQL Server Service Pack and uninstall SQL Server instance completely.
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