If it's the only one in the neighborhood that is turning early then it is either too dry or over watered. Both will cause the same effect. If other trees are turning early then it's simply due to the weather and you don't need to worry.
No. the condition of the leaves on any tree when autumn comes around depends mostly on the levels of moisture they recieved during spring and summer. If the leaves fall off without turning that indicates loew moisutre accumulation. If they turn all hues then moisture was abundant.
Not necessarily. It may be normal for your tree. Is the tree planted in direct sun? Is it getting the brunt of hot wind? Is it getting enough water? Try putting extra mulch around the tree and keep it watered.
No, the time of season that tree leaves change colour depends on the amount of sunlight, temperature and an individual trait amongst an individual tree's genetic difference. You have nothing to worry about.