I agree with Speckledhen. Commercial poultry facilities debeak the hens to prevent pecking each other (sometimes to death) because they are kept in small areas. I don't agree with debeaking, but I understand why the commercial facilities do it. I, however, see it as unnecessary in home-raised flocks. They aren't going to peck each other to death and I figure there beak is that way naturally for a reason. Some people file the tip down slightly so it is not so sharp, which I think is a better balance for backyard flocks (if pecking becomes an issue). In my experience (far more limited than many others here), the chickens will no peck each other if they have adequate space to move around.
Might, might not. Some people will say "trimmed" and mean "debeaked".
My banty cochin has a twisted beak. When it's growing a lot in the summer, I trim and file it down pretty frequently. But because I'm not taking it back very far, it grows back.
Beaks are like fingernails. The tips don't have feeling but take it back too far and you'll damage the tissue from which grows the beak/nail, therefore preventing all future growth.
A friend of mine once bought battery hens that had been debeaked. she tried to free range them on her farm and eventually had to give them away: they couldn't forage well enough to keep up their weights and lay.