Only really to expand on Gráinne's comment as regards the 'collecting' and 'roster development' sections - which are, as said 'distinct' although they are intrinsically linked - I would like to point you in the direction of the in-game Achievements > Battle Pets > Collect tab. There are a series of achievements called Raiding With Leashes, pretty much all of which can be completed via the auction house - if you have the gold/inclination - or by completing old raids.
A new quest will pop up once your first pet reaches level 3. It will send you to either Audrey Burnhep in Stormwind or Varzok in Orgrimmar. These trainers will offer a quest chain to battle specific Pet Tamer NPCs on each continent. Defeating each of these NPCs will reward a nice chunk of experience for your pets, as well a Sack of Pet Supplies (which has the chance to drop the Porcupette companion, among the always-useful pet bandages).
Since the same client is used for both our stress test users and our normal beta users, the name in the Battle.net App has changed to “Beta & Stress Test: WoW Classic.” If you’ve been selected to participate in the stress test, you’ll see this option appear in the Region/Account drop down menu so you can download and install the WoW Classic client in advance, but you’ll only be able to see the stress test realm when it becomes available.
Zygor was the home planet of the Zygons. (PROSE: The Bodysnatchers) It was known to be warmer than Earth and covered in water, which was in the form of lakes with a different mineral composition than those of Earth. There were also no icecaps on the planet. Native lifeforms of Zygor included the unaltered Skarasen and the Zygons. (TV: Terror of the Zygons)
For the stress test, all races and classes will be available for creation, but the maximum level will be set to 5. The test will also take place on a PvP realm, but since the starting areas are sanctuaries you don’t need to worry about attacks from the other faction if you just want to level up to 5. We expect to put a lot of people in the starting zones, though, and we’re looking forward to seeing what you all do as we test the servers under crowded conditions.
Each pet has 3 abilities it can use during a battle, but a total of 6 to choose from. They will also have a total of 3 active spell slots that show which abilities can be used during a Pet Battle. The first spell slot will already be unlocked, but the second and third will only become available once the companion has reached a certain level. Other spells will also unlock after reaching higher levels.
It was the experience of the game that brought pleasure and joy, and that's what a lot of us want again. Not the numbers. When I play Classic I want to go through the deadmines with people I like and overcome a challenge together and see myself become stronger as a result. I don't want to play Classic so I can say "booyah! That number is exactly the same as it was 13 years ago!"