I've got both RMFRP and RMC core books. Is RMC Spell Law competible with RMFRP 3 "Spell Law" books?
I've noticed many spell list that are practically the same (Essence Hand for example). Is it true for all lists?
Can the same lists be found in the two versions?
The only changes to the spell lists between RM2 and RMFRP was to fill in some of the empty slots on some of the spell lists. Other than that, RM2 and RMFRP spell lists are going to be identical.
Now in RMC, the spell lists are nearly identical to RM2, however the "Passive" spell type was done away with, and all Passive spells became either Informational or Utility spell. (and the new Phantasm/Illusion type was added). But this also means that the RMC spells also have those gaps in them that RMFRP filled in.
In hindsight, we should likely have filled in the empty slots like RMFRP did (but IIRC, the decision to not do that was made early on (i.e. the goal still being make it as much like RM2 as possible), before it was decided to get rid of Passive spells and I don't think it was ever revisited).