Each battle that you win will yield experience for each pet that participated. However, deceased companions will not receive any experience (so make an effort to keep them alive by swaping in a different pet). Experience gains are based on your pet's level compared to the wild pet. Defeating a higher level opponent will grant more experience than a much lower level one, but be ready for a tough fight!
Instead of sharding the zones, their plan is to shard the entire continent at launch. In Classic WoW, there are no dynamic spawns and questing in starting zones would quickly become annoying, so it's understandable that the game is all but fun when there are no mobs to kill, but layering will also cause you to see new players, every time you sign in to the game, which is a clear downside of the tech.
World of Warcraft (also known as WoW) players have highly requested the classic version of their favourite game. As with any game, changes and major updates are added over the years. Since August 2006, many changes to the game have not been received well: such as trivialising levelling up. The level cap will drop from 120 to 60, but contrary to how that sounds, it will be a far more grindy journey of fun and progress. The current developers have made levelling up very fast in comparison to the classic days, purely to focus on end-game content and raiding which many people do not enjoy. Prior to these changes, many people enjoyed the games for years whilst not hitting max level, something never seen in the modern edition of World of Warcraft. The levelling process was a journey, having fun with professions and the grind that is no longer found. Of course, there are countless other changes that will be reverted, as you might expect when comparing something from 2006 to 2019.