Not really. Any drive used for external USB is probably binned for that, meaning it may not have passed enough quality checks for higher-durability internal use.

If you want to be sure, dump and archive then yourself.

There was a project to archive all the 3DS stuff when that shop went offline.

No, split dns is having separate records for the same domain on internal and external servers.

Run a local dns. Have an entry in the local dns that points to the internal ip.

This is split dns. Merely having an internal server isn’t split dns.

Simple 1:1 audio stream is easy.

Groups, screen sharing, noise canceling, NAT traversal, mobile apps, and all those extra features people have come to expect are hard.