Yes you can, you use wifi. However, it will either need to be your own or in a hotspot that does not charge for the use of their wifi. Hotspots can be found in places such as pubs, clubs, train stations.
yes
Use a hammer
yes
YES
definelty not, however if you do not pay for unlimited internet, you will be charged for the use of the internet.
The apple iphone 3gs it rocks!!!!!!!!!!!!!!
It uses iOS
use the newest version on green poision
If you are willing to pay Roaming prices to AT&T for having called from Ireland all the time then yes but otherwise you can't because the iPhone 3gS can only be bought WITH an AT&T subscription. I know what you're thinking "the iphone 3gS is so cheap in USA" but unfortunately APPLE wants more money so they make it sim-locked to AT&T...
No
Yes, iPhones use a normal sim card.
well if the iPhone plan comes with internet u still have to pay even if u dont use it because they dont know that u dont use it, and wont care :/