Questions about mantona 3-legged suction cup holder L

Yes, the usual GoPro adapter is included.

It says so in the description: The Mantona 3-leg suction cup mount L for action cams, mirrorless, digital and compact cameras or smartphones offers you a very high degree of flexibility and safety. So yes.

If the camera has a 1/4 inch thread it should work.

According to my information, it should also be possible to attach this to the outside of the car.

Rather not I would say