I can answer questions 1 and maybe 2. If you have wireless at home, you can use your tablet without having an extra data plan.
As for #2, when out and about, unless you're in a location that has wireless, you would need a data plan to access the internet. For instance, my iPad has two options of accessing the internet. One is by wireless, and the other is by cellular data, and this is the one for which you need a data plan. I pay $30/mo to AT&T for this, but I love the portability (in the car, at airports, etc.) I can only quote AT&T's price.
That's half an answer. Someone else can correct me or fill in, as I am no expert! Virtual Geezer????
