Dear Flye,
Welcome to the forums. The answers to ALL the questions you have raised can be found by performing a "serach", using the search function on the yellow control bar a few inches above your post.
You will find many, many posts on the subject of Qatar Airways terms and conditions generally, and apologies in advance for having to wade through it all. However, the posts which answer your specific queries will also be intersperced with other "interesting facts".
Good luck and all the best!