This is not a helicopter. With the volocopter design, up to 4 of the 18 rotors can fail and you can still fly/control/land, and for contingencies there is a ballistic rescue chute.
Helicopter glide property is important because most are single engine. You could easily put several independent motor + battery partitions in this one.
Indeed. The 18 rotors in two concentric circles (6 in the inner, 2 x 6 in the outer) are each driven by an independent engine, and they're operated by many power trains that supply rotors on opposite sides. So, if a rotor fails (or actually up to 4), no prob, still controllable for expedient landing.
If a power train fails, same.
Those "power-free" landings require a collective pitch rotor system.
The volocopter appears to be direct drive fixed pitch so it wouldn't be able to autorotate.
It also presumably relies on counter rotating rotors to cancel out the torques, so loss of motors may require other motors to be shut down to prevent undesirable yaw.
I remain somewhat skeptical of these being practical beyond 5-10 minute fun flights around a field, but good luck to them.