Question about Segway-Ninebot F20D

Yes, if you only weigh about 50kg and only ride flat in Eco mode, otherwise it's more like 8km....

To be honest, no. Realistically, 10-12 kilometres without any major inclines. That's why I sold it again. It can't even manage short climbs either. Nothing under 350W really works. I would definitely go for this one:
Segway-Ninebot E2 Pro D
20 km/h, 40 km, 350 W

Yes, but only when it's flat. Slower uphill, of course.