Sam'sMom -
Welcome to the crazy world of optional gymnastics!
For each of the optional levels, there are specific skill requirements and prohibited skills on each event. These skills are categorized by the letters you referenced. The skills are all documented in the JO Code of Points, which can be purchased from USAG. However, as an experienced gym parent, my advice to you is to leave this area to the gymnast and the coach. Honestly, what the skills are and what thier value is just isn't something for a parent to bother themselves with. We have enought to worry about being the support system and the provider of ice, ibuprofen and tape.
Good Luck.