NO to the front brake question. That can make you endo, especially going down hill. You want to use both brakes, maybe slighly more emphasis on the back as you begin braking, but both in conjunction.
I had a "fishtail" when I was a newbie, where my back wheel slid from side to side while braking going fast downhill. Really scary. I was only rear braking at that point, and was really lucky not to fall. I asked here how to avoid that situation in the future, and was told use both brakes, hands on the drops while descending, feather the brakes, and bring my weight back so the rear wheel is making full contact. This has worked well.
Enjoy your bike! Hope this helps
