Can you still get into an Ivy League school or a similarily selective school if you do most of your extracurriculars junior and senior year, and/or if you’re transferring from a community college?
It probably depends on your stats, whether you are hooked (athlete, URM, geographic location – think Alaska or Guam, legacy), and what you accomplish in those ECs. It is typically harder to get in as a transfer (lower % accepted) than a freshman.
Neither scenario is unheard of, but neither is highly likely. The good news is that there are several hundred very good colleges you can probably attend instead. Apply to a few reaches, but you should also have a handful of matches, and 1-2 safeties you know you can get into, can afford, and are willing to attend.