Electric bikes - questions (Shenzhen)

Hi all,

For my day to day commute, I'm interested in using the electric bikes I keep seeing in the street. Those that you can also use as a bike (when the battery is dead I assume). I have a few questions about it:
1/ Do I need a chinese driver license for this?
2/ How and where do you charge those?
3/ How long does the battery last roughly? (1h drive? 2h drive?)
4/ How much does it cost? New or second hand

It looks convenient event if the driving here in Shenzhen seems "unusual" and so I should be careful driving it. If anyone has some experience or information about it, thanks for your help.

Cheers !