Back then, I made some sorts of mistakes; I'm stating this and clearly confessing my mistakes. However, the negative trust in my profile is affecting me on the forum; It's forcing me to create an ALT account and use it, which is also not allowed in this forum. Then what should I do?
You made those mistakes intentionally and that's why you have those negative trust on your profile. And, who said that having multiple accounts or alt accounts is not allowed here? Just read this rule:
18. Having multiple accounts and account sales are allowed, but account sales are discouraged.
Having multiple accounts and even selling of accounts is allowed on forum but account sales are discouraged and community doesn't like account sales and the ones who sell their accounts will get negative trust for that action. But, if someone who's a regular poster and who doesn't break forum rules then that person can create multiple accounts.
However, from ethical point of view, it's much better to tell everyone about your alternative accounts, don't use those for abusing bounties, campaigns, and games and rounds. As an example a famous and one of the most reputed member of the forum @LoyceV has an alt account which's named as LoyceMobile and that's a great example for you.