1) by 4/15 guidelines want you to hold no more than 3 total acceptances
2) you need to drop all other acceptances by 4/30. After that schools can see if you hold more than 1 acceptance and can rescind your acceptance without notice
3) CTE is school specific, usually 21 or 30 days before orientation, which is also school specific. However some schools have much earlier CTE dates. It is up to the applicant to know these dates and adhere to them. Failure to do so can result is loss of acceptance without recourse.