Getting accepted into a top level CS program.
time_management: 1. 0 years is the optimal gap. Time off counts against you. If you want to do this and don't see a strong reason for delaying, go in right now.2. You probably won't be publishing when you're working, and open-source projects are good but not enough to put you over the cusp.3. If you can get a research position, that'll be better for your grad school prospects than finance.4. I don't know the answer to this one.Caveat: I was in a math PhD program for a year, and CS may be different.