Vast numbers of high schools put all test scores on the official high school transcript sent to colleges. There are many colleges that accept the scores on the official high school transcript as the official scores and do not require test scores sent by the testing agencies.
As to how multiple test are used to determine admission, colleges come in three versions: (a) they use that test with the highest composite; (b) they superscore the tests and thus use the highest section scores from the multiple tests; © they use that test with the highest composite but all or a portion of the college may also consider a higher section score in another test (e.g., UIUC engineering uses the test with highest composite but will also consider a higher math score from another test).
Thus, taking another test and getting a somewhat lower score should not be considered a problem. Taking another test and scoring much lower than the first test could be a problem but not because of the colleges. In that situation, the ACT may investigate and invalidate the first test under a suspicion that something improper happen. ACT does not have to prove actual cheating, It can invalidate a test based merely on suspicion.