It's less of an issue for this device. The reason is that the motor is further from the axle than a hub motor would be. Thus, there's less force on the frame for a given amount of torque.

Depends on the bike and motor combo. Something like a mountain bike from the last 20 years would be fine, but I wouldn’t try and put one on like a road bike from the 70s or something. Basically anything that’s well built sturdy steel is going to be ok with the common sub kilowatt motors, but there are like crazy ones that will output considerably more power than that.

Also that’s going to be more applicable with a mid drive or a hub motor than something like this.

Interesting point. That might be the only thing this thing has going for it self. The angle of force is perfect even for the most fragile frame.

Weight

3.7 kg (including battery)

It only gives a boost for 50km.