Glad you're excited, and I can't wait to share more in the future!
1. Price is yet undetermined about the game, but at the very least there will be a sizable chunk (much larger than Prologue) available at launch for free.
2. While I absolutely want to eventually add these species options, do not expect to see them at launch. I want to make sure they're given the time and effort needed to really stand out when I eventually do create them.
3. Very very unlikely this will ever happen; though, alicorn characters may at least be referenced in certain parts of the story...