You do not specify a brand, but whatever serves as a pawl for the drive mechanism has seized and will not release to allow rearward movement.
Achermen steering gear
The larger wheels roll much easier over rough terrain. Smaller wheels can get swallowed by small divots and bumps where a larger diameter wheel will roll over the smaller divot's without dropping down in.
Either your brakes are 'ground' or something is wrong with the connection between the stick and the wheels. Go see a mechanic or car professional.
I think you might be talking about a backwards roll which is basically a roll from crouching where you lean backwards onto your shoulder and your arms are straightened, and you end up standing.
No. Bigger wheels roll slower than smaller wheels. They roll slower because they have a larger circumference and they take longer to roll. Smaller wheels have a smaller circumference meaning they go faster.
The simple rule is: always turn your wheels so that, if your vehicle rolls down the hill, it does not roll into traffic. The easiest way to do that facing uphill without a curb is to turn the wheels so that if the car does roll backward, it will roll off the road... i.e. turn them as if you were trying to drive off the road.
They roll, but they are really rather poor wheels. I would use something else.
wheels is a type of things that can roll. it helps cars to move
That is a given.
To roll on the ground.
It means you can roll - -