So you can only mount it upright. You can't mount it upside down because the column is only attached to the base. That wouldn't hold. It's best to buy the normal ones without a base for the wall. That's how I mounted a cable drum in my garage.

No, you can't, because the rod is only inserted

This will certainly be possible, it only needs a concrete base of about 8 cm. As I mounted the roll-up in the lawn, I took 2 garden slabs, glued them together with tile adhesive and buried them at ground level, then mounted the roll-up with metal dowel screws. It works perfectly. Good luck