Okay I guess everyone should have the chance to embarrass themselves and this is your time to shine today. There is no shame in not knowing something but I am surprised how confident you are.
Short answer: The only limitations you have on official are the Dino Level Limit which is 450/500 depending on the creature and 255 per stat and you wouldnt even need negative mutations for it, you can easily just get this with plain mutation stacking. There is a reason why Level limitation of 450/500 exists because wildcard is aware that people love breeding and spend their precious lifetime looking at dinosaur butts waiting for eggs.
Follow the advice of the others, watch some videos. I heard there is one channel that explains it quite well. Maybe read the wiki or talk to some breeders that did more than just mating two dinos and called it a day.