It is okay to jailbreak your iPhone 3g. The only downside to jailbreaking your iPhone is that you will loose your Apple warranty.
no, you dont. you can jailbreak your iphone and run it on tmobile's network, if you have a tmobile sim card. but on tmobile, you cant have 3g speeds, only 2g.
Simply jailbreak your iPhone 3G or iPhone 3G and install Cycorder.
No.
You need to download redsn0w to jailbreak your device.
Only if the iphone is a GSM phone with a SIM card... Otherwise if it is CDMA then no, you have to activate the other iphone.
No
PwnageTool 4.2
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.
The iPhone 3G already have a camera that is capable of recording video. The inability to record video on the iPhone 3G by default is a software limitation rather than hardware limitation. To record video on an iPhone 3G, simply jailbreak your iPhone 3G and install Cycorder.
iPhone/iPod Touch/iPad iPhone: 1G, 2G, 3G, 3GS, 4 iPod Touch: 1G, 2G, 3G iPad
Multitasking does not work on a iPhone 3G, You must Jailbreak your Phone to do that (Beaware that your phone would be very slow with Multitasking)