1. 14 speed only but you can alter sprocket and chainring size to get a lower or higher lowest gear- I ran 36/16 which was fine.
2. Mine was massively reliable once I'd replaced the Rolf cables for brake outers and gear inners- the liner on the Rolf ones got sucked into the shifter, seizing it.
3. See no reason why not.
4. 36T front, 16T rear- no issues but if you're a high torque rider rathern than a spinner that's not a recommended set up.
5. They are heavy. I feel the place for them is on lightweight bike, like an Enduro bike or normal XC bike where the bike will remain a normal weight and be a good ride. I had mine on a burly hardtail and it added too much to the weight- it pushed it too far into the "over 30lbs" category. I didn't find the location of the weight to be a problem- either in the air or on the ground.