Yes, can be used with the R7 without any problems.

Yes, you can, but then you have a crop factor of 1.6. The focal length is extended by a factor of 1.6 (160 - 640 mm).

Yes, that definitely works. But it doesn't work perfectly the other way round.

Full-frame lenses can be used on both camera types.
Only the other way round is not possible; S lenses, for example, lead to restrictions or undesirable vignetting on full-frame cameras.