You shouldn't be playing a romhack, just a normal Platinum rom. If you're freaking out over your Paras learning a move 2 levels earlier, you're playing the wrong game. But the entire game's difficulty, tons of evolutions, access to formerly inaccessible items and what levels pokemon learn certain moves are still redone. "Classic" in that hack means just means that more crazy changes to pokemon (such as type changes and stat rebalances) aren't included.
If you want to play Platinum how everyone else experienced it originally on the NDS, you don't want to play a romhack at all, you don't want to apply any patches.