Like a normal bike… low pressure water and a soft brush when needed, using added care not to spray pressurized water onto the electric components. Lubricant the drivetrain, etc as per a normal bike. Any good ebike will come with a detailed userguide with care instructions.
Depends on the type of ebike. Most Smartmotion city ebikes have a top speed around 35kph. Fast ebikes such as the Pacer can reach 45kph+ with moderate pedaling.
No. early ebikes had this feature, but it proved ineffective and the loss in efficiency uphill of a regen style motor depleted more battery energy than regen inputted when braking on downhill sections.
As long as your motor is below 300 watts, then you do not require a license and your electric bike can ride anyway a bike is allowed to ride.
An electric bike is simply a bike with a small motor and battery, so, anywhere you are comfortable riding a bike you can also ride an electric bike, as long as the electric bike is fit for purpose – note, if you are riding off-road, you will need a mountain bike styled electric bike.