It can work but be warned that long distance relationships require an immense amount of trust. This is my opinion from personal experience. The fact that the two of you cant see each other as often as you'd like is another factor to consider.
I think they depend on the sheer commitment both people are willing to put into it which will make it either work or end up in some sort of failure. But I feel you miss out on some of the key things about getting to know someone in person rather than saying starting a relationship online with someone you don't know. Maybe if you liked someone and they moved away then dated, but I guess it just depends on alot of things.
I can see the point of a short-term long distance relationship, by which I mean you plan to be together after a short while but I don't see the point of a long-term long-distance relationship because people need physical affection like cuddling, kissing and usually sex.
Hard to say. My best friend married her boyfriend for 10 years and they were in a long distance relationship. Never saw each other face to face until I wanna say the 7 year mark.
I especially don't recommend ldr for anyone under 18. That's just dumb.