That it doesn't run Windows 11 is a feature - that way, you can choose when to make the move, or choose not to, or choose something else entirely.

The title is wrong. It's not free - you need to give them your data, in the most literal way possible, or you need to otherwise use magic "company points" that you earn by giving up your privacy. That's not free.

Thunderbird is basically a web browser that executes whatever you want it to.

You have to possess the IP.

USB 3 is 5 Gbps, but real world never exceeds 400 MB/sec. 350 MB/sec isn't bad for a single USB 3 port.