After you buy it from a store, it is free to play after that.
You just need to buy the game. There is no online fee. It is free to play. Diablo 3 is free to play. There are no monthly fees unless you decide to use the RMAH.
No, it is not pay to play. The only cost is the one-time price to buy the game.
No. There is limited multiplay with up to 3 other people. It is free to play on battle.net
No. It is free to play.
All Diablo's 1&2 are free to play online but you must buy the game first.
You can't. It is provided as a bonus with the Collector's Edition of Diablo 3.
Yes, Diablo is in Diablo 3.
No, you just buy it like the other ones and you can play online for free but internet charges still count
Probably not.
Yes, of course people play Diablo 2: Lord of Destruction. And most people probably will until the release of Diablo 3. And even then, people probably might still play it from time to time.
Diablo 3 needs a constant internet connection if you want to play it, so yes it does need WiFi if that is what you use to connect to the internet. Hope this helps.
yeah man diablo 2 is a totally different game than diablo 1