No - buying apps has nothing to do with your data plan. However - you may need a data allowance to use some apps !
You can buy cell phone apps at the app store. The app store is available online and through your phone. You can check it out and select over a million different apps for your phone.
Only games. But for any other apps no
Assuming you have a newer version of Android OS on your current phone, when you upgrade to a newer phone, all the apps you had previously downloaded will transfer to that new phone. You can also download apps that can backup the data that is in an app (saving it to your external SD), and after retrieving the apps into your new phone, you can restore the data that was backed up. If your phone is rooted, you can use backup apps which can mass backup all the data that you have.
Turn on your phone.
Definitely yes.
I think you do. Although, when you turn it on for the first time, there are some default apps that come with the phone.
Yes, if the apps are free and you are able to use a wifi connection if they require internet connectivity
It depends on how much you want on your phone.
Yes it is a smartphone because you can buy apps for it and therefore it is a smartphone... :)
Yes that is the default way of buying apps on Android Market. If you are on contract it will be charged at the end of the month
Phone apps are games, music, or videos that you can get on your phone. You download them and they go directly to your phone.
The Andriod Ally is a good phone for apps.