A majority of D&D characters don’t use feats

Can you use a longbow in melee to get Great Weapon Master and Sharpshooter in a single attack for +20 damage?

So a darkvision party, who refuse to bring torches or use Light, should still be getting disadvantage in dim light?

It possible for beholder to replace it’s central eye with Vecna eye?

Why are all the half-orcs, half-elves, etc always half-human?