Call it a Nacra 20 or Inter 20 or N20 or I20. Not sure there is much difference between a N20 and I20. It is not an F20.
In terms of removing the Inter- I would use a razor blade (I believe it is just a vinyl graphic) and then use acetone to take away the residue. Problem is that the Inter 20 logo will likely still be "burnt" into the hull even after cleaning it all up. so... you might want to consider leaving it although I am sure someone has a way around the burnt in issue (but would require a ton of polishing maybe).

I think you should be able to find a used decent spin for the 20 without too much problem. If you buy a spin pole, you will need to buy the hoop as well that goes on the pole. This would require a 3 patch spin. You might be able to find a used pole with mid snuffer or an end pole snuffer set up (mid pole hoops are the same I believe for all the Nacras regardless of length of the boat). The end pole is less ideal but you should be able to possibly get one of these older setups cheaper (this would require only a 2 patch spin).

As far as the tramp- depends on the status of the tube in the hull that the bolt rope for the tramp runs in. Could be the tramp or the slot. Others have more experience with this than I do.