You can have multiple DC for a domain.
If you mean to do a migration your correct step should look that way;
I would add another step, 4.1, to test if the replication and all active directory is replicated correctly.
The part that is not wrote is that even if you have two domain named the same way, and account named the same in both, the GUID will not match,...
Long story short:
Prepare the destination tenant: create all the same users with
required licenses, groups, resource mailboxes and shared mailboxes
assigning them some temporary domains for example onmicrosoft.com.
Assign members to groups, recreate mail flow rules if there are any
in source tenant etc.
Then in the source tenant you remove the domain you ...