The one from Galicia (the round) and the one from Castilla & Leon. Individually numbered and made by the same people that make the ones you see on your walk.
Hi Nino
I think a google search for bike rental shops in Ferrol might be a possible solution in answering your first question unless anyone here knows.
As for cycling to qualify for your compostela certificate you must prove you have cycled at least 200km on your camino (its 100km minimum for walkers).
Good luck should you take the plunge
Chris
I presume you know this already, but the Camino Ingles from Ferrol is just a bit over 100 kms which means doing it on a bike would not qualify for the Compostela. I suspect it would also be a very short trip - perhaps only a couple of days.