Since your current hardware version is V2, you can only update firmware of V2. Different hardware versions can't be updated.

How about if you connect one client to RE200 via a cable? Can you get the wired connection through RE200? try to restart your router and range extender.

HS200 and HS220 are both two-way switch, HS210 is three-way switch(with 2 traveller lines) which does not support 4-way switch, so HS220 could replace HS200, but not HS210.

It seems it only supports FTP..

If you use IP address to login, the same username and password are correct? have you tried with different clients?

When you plug USB into your PC, can you see the folder? Make sure the format of USB is supported by the router. better to email tp-link support for further help directly which is more specific.