Should I follow up a job rejection?

It's worth considering that they don't want to hire you again for whatever reason. To make a b.s. excuse such as not answering 2 questions as well as the #1 guy - when they know you can do the job and have worked there before - tells me they just don't want to hire you back. It can't hurt to follow up, but if you don't hear from them again, just move on.