No. You are unable to play the role of a pup in WolfQuest either in single player or mutli-player.
yes.
Currently there are no plans to develop a third episode of WolfQuest.
No, the only new features to 2.5 are weather and time. It's not like a whole new episode.
Currently you are not able to play as a pup in WolfQuest due to the amount of funding/time it would take to develop.
To get the albino pup you must have 50,000 experience points before the pups come. I suggest looking through the WolfQuest forums.
Currently as of Episode 2.5, you've completed the game when you've reached the Rendezvous Site with atleast one living pup.
There is only 1 wolfquest quest in wolfquest episode 1 but in wolfquest episode 2 coming this December 2009 there will be multiple quests!
You can get episode 1 and 2 at the Wolfquest page linked below.
No you will be unable to play the role of a pup in single player or multi-player.
A fourth den and a white pup
Just keep feeding the pups.