No, you cannot have group chats on FaceTime (as of September 2014). FaceTime is a video calling service Apple provides to users of their devices such as the iPhone, iPod Touch, and iPad. You may FaceTime with only one other device at a time.
No software is required to use Facetime on the iPhone 4. It is required that you be on a WiFi connection. Facetime can only be done from one iPhone 4 to another iPhone 4.
If you are using Facetime on a jailbroken iPhone then it is possible to Facetime chat with out using a WiFi connection. Simply go into Cydia and search for a package called My3G. This app allows you to trick your iPhone into thinking is it on Wifi connection allowing for Facetime chat over a 3G connection.
An alternative to using Facetime would be Skype. Skype can be downloaded in the Apple App Store. Skype is video chat that can be done from iPhone 4 to iPhone 4 or iPhone 4 to a computer or computer to computer.
Two and two make four. Makes is for a singular subject, make is for a plural subject. When in doubt, try substituting the two twos with other words, like "leaves and grass turn brown in fall." You wouldn't use "turns" in that sentence, which is structured like the original sentence.
Facetime doesn't yet support conference calling
yes, of course they do. Aren't you talking right now? Only deaf people, can barely talk. Most of the time is is mumbling.
You only need to set up an account with the iTunes store if you want to download apps. It is free to set up an account. To set up an account and to use FaceTime you need your email address.
I have been looking into that as well. As far as I know they have not set any pricing for that feature. I imagine it will be a cost per minute thing. At this point it is still in beta mode and you can renew it each month for free.