If by "restart" you mean "reboot", yes; several times. This is necessary in order to download the jailbreaking code on to your device.
It should be noted, however, that unless things go very, very wrong, a jailbreak will not cause data-loss. All your existing applications and settings will still be there after the jailbreak.
No it will not
Jailbreaking allows you to customise your device considerably more than Apple allows you to by default. The customisation aspect of jailbreaking is what the majority of iPod Touch users want when jailbreaking their device.However, do note that jailbreaking your device will void your warranty. This means that should something go wrong with your device Apple will not fix or replace your device.
Jailbreaking is the term used when cracking an iOS Device while Rooting is the term used for cracking an Android Device.
You can root your iPone 4S by jailbreaking your device.
Reboot means restart. It does take awhile in the Jail breaking process.
Yes by jailbreaking your apple device
altering the factory software so you can download stuff from other places not only of the app store. jailbreaking can be dangerous for your device
Not that I know. Sorry.
Music-wise, jailbreaking does not get you any free music that you wouldnt have had without jailbreaking it. You can find free music anywhere online, with or without a jailbreak. Jailbreaking does not get you free music, but does get you mods, apps, etc.
YES, "jailbreaking" or ANY type of modifying the device does VOID ALL warranties from apple. [But in my opinion: I don't give a flying f*** for warranties]
When Jailbreaking a device, if the device breaks, the specified device cannot be taken back to apple unless it is restored. Jailbreaking can also make battery life worse, as more 'daemons' are running, such as themes, and back-grounding applications. However, Jailbreaking allows you to download app store applications for free, theme your device, and do so much more than before! The pros definitely out-way to cons! If your device screen breaks and you have to send it to apple, simply plug it into iTunes and click the restore button, which removes the jailbreak.
No... not at all. It only applies to a jailbroken device.