First requirement: That you be resourceful enough to find these answers on your own. The easiest and most practical way would have been to see the official Web site.
1. Yes. Basic requirements are 18 and a US citizen. Realistic requirements are to have a four-year degree (though you may qualify with a two-year), have a a good track record of community service and be in relative good health. The medical process can take a year and can be expensive if you don't have insurance. You can go to the official Web site and search for 'competitive candidate' to find out more.
2. No. You can state a preference for a region (as well as tell your recruiter where you would prefer not to serve) but there are no guarantees. In theory, you should be willing to go wherever you're needed. (In addition, some regions, such as South America, have unwritten requirements, such as knowing Spanish.
3. A little. Again, spelled out on the site. For when you return, the federal gvt puts aside a monthly amount (I forget what it is since it increased since I served in 07-09, but you can check it) that comes to about $7k before taxes. It's not enough to do squat, really.
While you are serving, you get about enough to live on. It varies from country to country. Mine was 2000 Moroccan dirhams.I did fine on my living allowance but there were others who had to supplement it with money they'd saved.
If you are considering joining PC, you need to do a lot of research. If you are not capable or willing to do your own research, you aren't a candidate. Peace Corps is more than "helping people." It's about succeeding with little help or backup, and if you felt you had to turn to the public to answer such basic questions, it's a red flag. (I say this not with a mean spirit but as someone who has been through it.)
After you read the official page, go get the book So You Want to Join the Peace Corps - What to Know Before You Go. It is the best information you will ever see on the application process.