It is actually 1-200 in the Hoenn Pokedex. It includes new Hoenn Pokes and some old Kanto Pokes too, so going from 252 on isn't very accurate. Yes, the Regi's are included in the Pokedex. The only two Hoenn Pokes that aren't are Deoxys and Jirachi. Once you have all 200, and you show Prof. Birch your Pokedex, you get ONE Johto starter.
BTW - Questions like this should be asked in the Simple Questions thread up at the top.