Your height: 5'1" to 5'5" (153 to 164cm) approximatly (?).
Frame size = 19in/48.5cm
Comments:
Mountain Bikes: they are sturdy and designed to go everywhere including off-road. Good for rough riding. In general heavy and with deep thread tires slow on paved roads. Not good city bikes unless narrower and slick tires are installed.
12 speed: good to go just about everywhere except very steep hills. The range of different ratios are more than enough for most people. There are 2 front chain rings and 6 rear gears. - Derailleur: Falcon
Tires 26 x 1.95: wide tires, deep thread, all terrain.