MS SQL Server 2012 R2 SP4 MS SQL 2012 R2 SP3 is out of support.  We were having issues with DB Cluster which is 2012 R2 SP3 and Microsoft said it’s not supported version. We need to go for SP4 to have support.
I suppose it’s not just MS SQL version, Service Pack is also associated.
Can you correct me here?
...I suppose it’s not just MS SQL version, Service Pack is also
associated.

Yes. You can read the lifecycle policy on service packs here.

When a new service pack is released, Microsoft provides either 12 or
24 months of support for the previous service pack, varying according
to the product family (for example, Windows, Office, Servers, or
Developer tools).

As a side note, if the product is out of support then the service pack is also out of support, regardless of this policy.

When support for a product ends, support of all the service packs for
that product also ends. The product's lifecycle supersedes the service
pack policy.

For your case, the SQL Server 2012 SP3 lifecycle policy can be found here.
The SQL Server 2012 SP3 support end date was on 10/09/2018

Note that starting from SQL Server 2017, the servicing model was changed to only CU's and GDR's when needed.