It seems that G2 has 103 unique levels and these levels are fliped or rotated in 4 directions for a total of 412 different levels. So if the game gose up to 999 then all levels are repeated 2x and some 3x.
the same gose for the treasure rooms and secret rooms.
I will only do the 103 unique rooms ( I will not do the othe 3 rotated ones) as well as the treasure rooms and secret rooms.