Gernerally speaking, the name will be the same as your main router after you configure the Range extender successfully. Try to check whether the RE is working now. If no, you may need to reconfigure...

we can plug a USB 2.0 drive to that port to share the file. You can have a look at the below link: https://www.tp-link.com/us/faq-1527.html

when the router lost connection, is the main modem working properly? Is it the latest firmware? update the FW firstly. If it's just the wireless issue, try to set a fixed wireless channel.

I also have a UH720 while it's very convenient for me. Perhaps I haven't connected all the 7 USB ports, there is no any issue so far. One thing like you, it seems it will turn off sometimes even I...

I consulted a same question before and tp-link told their adapter does NOT support wifi direct feature.

TC-7620 can only be used in USA, so it doesn't support in euro, Germany.