Hi I'm considering jailbreaking my iPhone 3GS I want to know a few things:
1. What are the benefits of jailbreaking?
2. What am I able to do that I couldn't do with an unjailbroken device?
3. What is Cydia and what does that offer?
4. What jailbreaks are available?
5. Can I reverse the process easily without ending up with a bricked phone?
6. How legal is it?
1 and 2 are essentially the same question. If you could do it with the unjailbroken device, it's not really a benefit of jailbreaking after all.
With that in mind, jailbreaking allows you to install apps and tweaks that Apple hasn't signed. These range from enhancements to the text messaging system to call screening to adding swiping functionality to allowing for themed appearances etc.
Cydia is the "iTunes Store" for jailbreakers. You'll essentially carry two stores: one for jailbreak applications and the one you've always carried. Like Apple's store, Cydia contains a combination of free and paid applications.
Jailbreaks available depend on your current iOS. If you're on 6.1.3, there isn't one. If you're on 6.0-6.1.2, evasi0n is your best bet. Prior to those builds, you'll have the least amount of trouble using redsn0w. That can be found here:
Dev-Team Blog evasi0n is at
evasi0n iOS 6.x Jailbreak - official website of the evad3rs
To reverse the process, simply plug your phone into iTunes and tell it to restore your phone.
It's as legal as breathing. Apple frowns upon it and voids your warranty if they find out. However, a quick restore hides it from them. I'm also not sure how much Apple is still servicing the 3GS to begin with so I'm not sure this is a factor in your decision or not.