There are several major steps:
Mount the LUN or LUNs as a filesystem
Have the required namespace
Mount the CACHE.DAT in Cache. Look at ^DATABASE
Have the required global mappings.

My suggestion is to install another instance of Cache on the server.
That way you might be able to update the cache.cpf using the one from the old server as a template.

This is a pretty complex task.

As a guess you have more mirrored datasets then expected. I have seen User get mirrored for example.
What does this show on the primary?
d ^MIRROR -> 1) Mirror Status -> 1) List mirrored databases

If both TESTTC01 and TESTTC02 existed before starting, your refresh process is also overly complicated.
You should be able to shutdown TESTTC01 & TESTTC02, copy the file from TESTTC01 to TESTTC02, start TESTTC02 and do a Activating and Catching Up Mirrored Databases. If you have a backup or snap of the file you don't even need to shutdown TESTTC01.