Can I become a 2100+ rated player in 2 years if I train for 15 hours a day? I’m 15 years old, and my FIDE rating is 1674. I’ve been playing chess since I was one and half years old. If I train, say, something like 15 hours a day and play in 20 tournaments, is it possbile for me to become a 2100+ rated player in 2 years?
To predict someone's progress is very difficult. It depends on so many things: "chess talent", how you practice and train, opportunities to play tournaments (not too weak, not too strong), etc...

A couple of years ago, the author of following blog tried to become a grandmaster: http://roadtograndmaster.com/ and http://roadtograndmaster.com/?p=11

Maybe this blog can give you some information, ideas and tips. Of course, your situation is different, for instance, you are 10 years younger than the author of the blog.