I tore my ACL MCL and lateral meniscus on a double up (ACL was completely gone) and my buddy did his ACL partially in the same month. He got his with a sort of "shrink wrap" procedure and it ended up tearing all the way shortly after. I did a hamstring graft (from the choices of that graft, a patella graft or cadaver ligament). I don't regret the hamstring graft at all but i would do a cadaver ligament next time for sure as the recovery is a little easier. A lot of people talk about how they are only 60-70% of what they used to be and blah blah blah, it's mostly mental and that takes time to get back. I still work mine out 3-4 times a week with select work outs out side of riding.
As for your knee that is currently jacked, I can honestly say that your probably gonna end up doing more to your already torn miniscus which will lead to arthritis and constant pain down the road. Is it worth for one competition? To me, no. I ride outlaw and ride my ass off into the flats riding hard and often, so unless your Danny harf throwing a knee brace on with no ACL to win the x games cuz it's your paying career, I don't see it as worth it. Not to mention if it tears your meniscus further that'll be more of problem than an ACL graft. ACLs are replaceable, meniscus isnt.
I use DonJoy knee braces and they're legit. If it fits a little loose when wet get a neoprene knee sleeve like some basket ball playerswear and use it under to help out