@shocking I'll send you a pm real quick about the fastest / easiest way to get around 40k nx quickly.
Yes it's safe... Just don't bother to do ones where you need to download / install a file. Also create a new email account for using on them, otherwise you're going to get spammed like hell on your normal one. Though that's pretty much common sense.
Haxz you must know next to nothing about computers.... anyway some tips.
Anyway there are a LOT you don't need a credit card or anything else for, keep in mind you're going to find more that DON'T work then that do work. When I fill mine out, I use legit zip code / city / state, for phone number just put in the first six digits of what yours is then make the last four like 1234 etc ex - 777-666-1234