Yes, but only if you unlock you iphone
No
any AT&T phone that can take that sort of sim card.
Yes, Yes you can.
You put a sim card in it.
Yes as long as the phone is att and has a sim card slot
If your 3GS is locked, you can't insert a SIM card.
As long as it is AT&T, yes.
the iphone has a sim card which slots in the top of the iphone. to get the sim card tray out you have to use a pin or the special tool it came with to open it.
Yes it can be swapped. I actually swapped my razr's sim card to my iphone. Nothing happened. It works perfectly.
Yes, you will have access to all the features. It doesn't matter what SIM card is in your phone because the phone needs a SIM card, given to you by a carrier, that is supported by the phone to operate. Just put the SIM card in the HTC Wildfire and put it in the iPhone.
Put sim card into nokia, go into Contact list -OPTIONS > MARK ALLOPTIONS > MOVE SELECTED (Choose sim card)Put sim card into iphone...SETTINGS > MAIL, CONTACTS, CALENDERScroll down a bit > IMPORT SIM CONTACTS ;)frisky
Of course, the iPhone 3G and/or the original iPhone will take any normal sim card; the 3G iPhone will take the 3G sim as well.