Yes, Yes you can.
No
any AT&T phone that can take that sort of sim card.
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.
Yes, but only if you unlock you iphone
As long as it is AT&T, yes.
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
Sure. As long as your iPhone model has the SIM Card slot. Just make sure your LG uses Micro SIM Cards, or else you just have to cut your SIM Card to fit.
Assuming the SIM card is the correct size for the iPhone (ie not a micro SIM) - there's no reason why not. Since you say it's unlocked - it should accept any networks SIM card.