NO. You need a connection to "log in" but if you did that at home where you had one, there should be no reason why you cant fly. If you logged out and then tried to fly without internet thats a problem If you were logged in already you shouldnt...
The DC Adapter for the M3Pro battery charger has two USB connctions, typically used to connect a battery tray and the remote at the same time for charging. I'm wondering if anyone has gotten their hands on a second battery tray and tried using...
Not sure where you are getting the link for it but the app can be found here
https://www.dji.com/uk/goapp
Use apkmirror website to get an older version of the app, you may have to try a few to find one that works