If I want to place a classification with the ESRB standards, I need a permit from the ESRB or have some authorization or copyright.
Im no expert but i would guess that you would need to submit your project to the esrb to get a certified rating from them. That would probably cost a lot of money and be extremely complex. if your a not a major developer i dont think id even bother.
*Not legal advice this is only my thoughts on the matter.
You’re not allowed to use ESRB ratings without getting ESRB rated.