Philips Sonicare ProtectiveClean 5100Sonic electric toothbrush

In which countries is the Sonicare app available?

Can I use my Sonicare AirFloss charger to charge my toothbrush? 

How does the brushing guidance work in the Sonicare app?

Why is there a gap between my brush head and handle?

Can I use my Sonicare charger with other toothbrushes?