I assume that the materials you submitted will stand up to regular scrutiny. Your lost seems to suggest you have something to hide. We probably hope their is something in our pasts we prefer others not to know, but there isn’t anything disqualifying for anything. Something in 8th grade surely isn’t sufficient to disqualify you from college.
Borrowing trouble is not a helpful strategy. If something is asked in the future, you will have opportunity to respond.
I highly doubt colleges run in depth background checks on all applicants. If someone reports something incriminating to the admissions office, they do sometimes take action. Read about the Harvard applicants who had their admissions rescinded due to offensive memes this year.
I hear that if you claim to have done something amazing (like publish a book/start a non-profit/create a popular website), then they will check it out to make sure that it is true. If I were you, I would delete all that you think that you’ve posted and is incriminating, if you want to be on the safe side.