yes you can you use green poison rc6 for untethered jailbreak.
Ziphone, google it :)
Absinth
By using connecting your iPhone/iPod to your computer and running some software. A process to use non-propietary software on the iPhone/iPod.
If you have the iPod Touch 3G or 4G (current one), an iPhone 4 (not the iPhone 4S) or iPhone 3GS, or the original iPad (Not the iPad 2) then use redsn0w 0.9.10 to jailbreak. If you have an iPad 2 or, iPhone 4S, you cannot jailbreak it on iOS 5.0.1 yet
It allows you to run Un-Offical Software on your iPhone using Cydia!
Modded software that allows the user to put third party applications on the phone.
Yes you can you just need to download the correct jailbreak software.
Jailbreaking can only be done for iPod Touches and iPhones. No other phone has the ability to be jailbroken. For an iPhone, you need to download a software from the internet to jailbreak it.
Us Jailbreak me on the iPhone 4 if you have the firmware 4.0
Yes. Just sync your iPhone with your computer and download the 2.2 software. The new software should wipe out the jailbreak, so just re-install it.
No but you can jailbreak an iphone or ipod touch but they each have different sites to jailbreak your ipod/iphone
To put an HTC theme on an iPhone 4 you will have to jailbreak your phone and use appropriate software to download the theme.