Allright, guys. Sorry to bother you again, but after successfull start with remapping (working on a hack), I decided to insert some new sprites and change some pokemons. Well, worked without problem. Oshawott was in the game and so was Snivy. However, when I opened FSF to find some space for Tepig, I was given some space as usual, but this space is not chaning. Can't get new set of free bytes for inserting another sprites.
I thought that my rom (FireRed) may be damaged somehow, so I tried another one, but after inserting same sprites, same problem popped up.