Are u allowed 2 ride little 50cc gas scooters on sidewalks in devolpements without a liscense?

Sidewalk = side + walk.
For people to walk on the side of the road.
So they don't get run over.

Need a law to tell when something is stupid?

And in a residential area where children play?

depends on the laws in your municipality. some areas allow it some dont. if you are in a gated community with a homeowners association, you should check their by-laws. if it is allowed in your area by your city govt, your homeowners association may not allow it.

No. It is illegal in every state in the US to ride a motorized bicycle, scooter, or moped on a public sidewalk, with or without a license. The only exception is for handicap scooters and power wheelchairs.

in my state it is legal to ride a 50cc and under on the roadway w/o the motorcycle,endorsement, however, you do need to have a valid driver license.
as of last year it was still legal to ride a motorized go-ped on the sidewalk as long as the city did not have an ordinence against it(this w/o a license). the state law was vague, and open to individual city's interpertation.