Not for water activities like swimming, it 

Please check sub-table 2 for the operators corresponding to different countries, please update the operation according to your site. For example Germany is: T-Mobile, Vodafone, E-Plus E-+ Mobilfunk 

1.I’m sure it’s glass - when I clean mine with isopropyl alcohol they make that ‘squeaky’ noise you get with glass rather than plastic, and they’re more resistant to scratches than most plastics are. According to manufacturer website K & F use German optical quality glass so I’m sure they would have been called out for that a while ago if it wasn’t true 2.I drop one last year and it broke like glass ..I’ve found them easy to clean and well made. 3.Looks and sounds like glass to me 4.HD optical glass 5.As far as I can tell it is glass. Excellent optical qualities 

Yes, it charges them quickly and then the light for that slot turns green. To me, that's an indication that it's going to lose power because the battery isn't hot the next day. (No, they don't need to be charged overnight, they're fast.) 

1. Make sure the camera is powered on and the router's network is working well. 2.Reboot the camera. If the camera is still disconnected after restarting, please remove the camera from the app and then reconnect it.