Question on facebook

[Ildebrando]

Hi all;
One friend asked me to create some facebook accounts because he is not able to do it (he is not a boss with the PC…).
Ok, no problem, I think: some new email accounts, different names and surnames and everything is ok.
After the first account facebook ask me for the confirmation with an sms, maybe is my IP address?
I change email, change IP, delete the cookies but it is the same, it always ask me a phone number and the confirmation by Sms.
If I change browser I can create a new one but at the second the problem appear again.
I reset the pc but nothing: I think that if I change the pc maybe I will have the same problem.
At this point it is a personal issue for me : how can facebook understand that it always me that create a new account and not another person that is creating his first account?
Do you know which parameter facebook use to ask or not this phone number?
Another doubt: if you are in an internet point how do you connect? everyone must insert his mobile number?
Thank you for your help.

 

[iCrank]

Moved to appropriate area as this isnt a phone issue it's a pc concern.