Q: What does iPhone 2G and iPhone 3G mean?
A: 2G refers to the GPRS and EDGE wireless connectivity of the original iPhone while the 3G refers to the upgraded 3G wireless connectivity of the iPhone 3G
Q: What does activate, unlock and jailbreak mean?
A: Activation is required on all new iPhones, unlocking allows the iPhone to be used with any GSM provider and jailbreaking allows the running of third-party applications
Q: Can I unlock the iPhone 3G?
A: Not currently with software, but you could purchase a Turbo Sim
A: Yes, see here, this will enable you to install a memory-resident unlock software driver to use your iPhone 3G with any GSM provider (yellowsnow)
Q: Can I jailbreak a iPhone 3g?
A: Yes, using software, see link
Q: Can I activate, unlock and jailbreak the iPhone 2G?
A: Yes, see link
Q: Which is better, the iPhone 2G or the iPhone 3G?
A: It really depends on what you want, the iPhone 2G would be good for users who do not need the higher speed wireless connectivity and the GPS functionality. Remember that the 2G runs the exact same firmware as the iPhone 3G and thus offers the same functionality in terms of the firmware.
Q: What is firmware and which is the best?
A: Firmware is the iPhone operating system. Currently, the 2.2 is the latest and is generally considered the best firmware for the iPhone 2G and iPhone 3G. Some diehards still run 1.1.4 for the iPhone 2G, although this is limited in terms of functionality, namely access to the Apple App Store.
Q: Does unlocking the iPhone 2G or 3G slow it down?
A: Not at all, in any way. However, loading a large number of applications can have an effect on the speed of the iPhone, so it's best to keep the number of apps to the ones you need. Feel free to test them out and uninstall them if you want though!
Q: Can I upgrade my unlocked or jailbroken iPhone to the latest firmware using iTunes?
A: Stop, before you do that it's best to check, as sometimes you can upgrade (note upgrade, don't do a full restore) but sometimes you could do damage. Check out iPhone Dev or iClarified before you do this.