A:AnswerI have had that happen. What I do is use a usb mouse to get control of your computer. Click on the little blue tooth symbol on the top and click the mouse connection and tell it to connect. When it does, you can disconnect your usb mouse.
A:AnswerYes you can. You could pair any bluetooth device as an input device. If you like and are used to using the trackpad on your MacBook Air.... You could pair a new Apple Magic Trackpad or to answer the specific question, you could pair an Apple Magic Mouse.
A:AnswerYes. In fact, my grandson uses this Apple mouse with his Windows 10 PC. I didn't think it would work but he connected it right before my eyes and uses it every day. So it definitely works.
A:AnswerIt will work without a usb hub as long as you have the latest version of iPadOS. The March release includes Bluetooth mouse support. You can charge the mouse with usb, but it is Bluetooth only for use.