I think i was in 6/7th grade when I beat it. I had all the patterns down for every level
2 (dam)- getting in the lake was easy, but that 2:20 time limit was tough. Additionally, sometimes, the lake would spawn currents which would make it difficult to swim. Once you figured out the pattern, I could get through with about 20 seconds to spare
3- City: You got to drie around in the van and run over soldiers which was fun. I would go into certain buildings to get 20 missiles for the van and then stock up Mike and Raph with 40 scrolls each. The scrolls were uber powered and would come in helpful in later levels. Meka turtle is easy, hit him with a few scrolls and hes dead.
4- Airport: You had to go in the manhole covers in a certain order, but the level itself wasnt hard aside from the instant death spikes near the end. Big Mouser was easy. Stand right under him with Donatello and aim up, e cant hit you.
5- Base: The technodrome boss spawned at one of three random locations, there were a few pizzas in this level so Id try and heal up. Technodrome boss, Id fire scrolls to take out te weapons and then stand on the treads and hit the eye
6- Tecnodrome: Holy crap hard as balls. Random flying things that fire lasers and you cant jump over, and dont get killed by a scroll. I usually took a guy that had full health and just try and run through. After that Shredder was easy.