Not all of them do, but those who have will usually be equipped with a type of caliper brake known as an U-brake.
The rules aren't the same everywhere.
In My country, the law is "one brake separate from the drivetrain".
Meaning If you have a coaster brake, you also need one other brake.
If the bicycle is road legal(has brakes, lights, reflectors) - sure.
depends on the bike and the brakes. Go to www.parktool.com or www.sheldonbrown.com for more.
If you're talking about looks then it's all about personal taste, and IMO brakes are so darn useful that I'd keep them on no matter what. If you intend to ride in traffic they're required to make your bike legal anyhow. Structurally your bike is fine with them.
Disc brakes and drum brakes.
if your bike is a u, v or disk brake the cable is probably to tight or if you have hydraulic brakes of any kind your brakes will do this you just have to deal with it
any bike store
Mechanical disc brakes.
Yes
Brakes are designed to stop things from moving, therefore making it difficult to move a bike that has its brakes on.
If it's a public road, that anyone is allowed to use, then the bike has to be road legal (lights, indicators, mufflers, brakes, emissions...) and insured, and the rider will need a driver's license.
It depends if you have a 3 piece crank, spokes, brakes.
Yes