Yes, that should work. We live on quite a slope.
If it's really steep, I zigzag. But most of the time I get up at 16 km/h

Yes, this is no problem. With a maximum payload (> 100kg), the maximum speed may not quite be reached. However, it is important that the tyres are well inflated! The rolling resistance should not be underestimated.

Should work; it's also a question of the weight to be transported😎