Ooh, good questions!
- I'm still not sure of how I'm going to ask you to obtain Pokemon in this RP, since it is a little different from others. But generally in RP's the GM (person in charge, game-master) will give you a list of Pokemon you can catch in a certain area. Then, you right a detailed post finding, battling, and then throwing the Pokeball at the pokemon. In the GM's next post, they will tell you whether or not you caught the Pokemon.
-I'm not sure how other people do it, but in this RP, one of your missions will involve writing about it hatching.
-Battles are usually had between one of the main characters, and an NPC (oersin who isn't played by one of the RP'ers). So in your post, you would be able to choose who wins the battle. However, if it is between two RP'ers, either they decide who wins on their own, or I pick based on who wrote the best post. Battles that are better written will give your Pokemon more experience, and it will be closer to getting more moves and evolving.
-You can stop an RP post whenever you'd like, as long as it is a good length and has good details. Sometimes, certain chapters or mission will have a specific amount of posts you should make to complete the mission (like, 1-2 posts, or 2-4 posts. It depends in how much there is to do in the chapter)
-I kind of said it before, but usually the GM provides a list of Pokemon obtainable, and the RP'er (you) can pick which one they want to TRY to catch. Usually there will be Pokemon that are harder to catch than others, and will require a better post.
-I'm not too sure what you mean by this last one. xD But basically in this RP I will be giving the RP'ers different missions to complete. They will have to interact at some parts, and eventually it will turn into one main plot, which is a secret right now. ;) Feel free to make some side-plots of your own, though, it isn't only doing just what I say, and you have a lot of room to explore!
I hope those answers helped. To be honest, I'm not the best at explaining things xD