deleting all apps and settings

I have 2 iphones ( 5 and 4s ) with the same apple ID.I want to give away the  the 4s iphone.I need to  reset and delet all apps and settings from 4s before I give it.

since both devices sync wiith the same app ID , if I reset and delet on 4s  , will this delet all information on my I phone 5 as well? 

I did backup both on my computer( not with Icloud) with I tunes.

when I activated the Iphone 5 with I tunes for the first time, I used restore from backup ( that I had from I phone 4s)

my concern is not to lose my contacts and mail.

thanks