Thank you so much! It took some Googling but I figured it out!
I'm stuck in act 3 now tho. I used the syringe, but I can't figure out the next objective (apart from getting the lvl 3 card - which I can't find).
I also believe I found a softlock - if you discard the L2 card after passing through to where you get the swimsuit, there's no way to get back out.