in reply to
fourth digit should not match digit "2"
See the answers you (or your cohort) got to Regex for last digit should not be "2" and adapt them. Maybe consider reading your course material, and/or perlre or perlretut.
The same name on every site (unless it is taken already)
A different name for every site
The same name for sites I don't care about, but different names on sites I do care about
Different names for sites I don't care about, but the same name on sites I do care about
The anonymous account
Someone else's username
Root, after hacking into the site
Results (236 votes),