Can handicap use a float device?

Yes. If you mean are they allowed then yes but I guess it depends on the disability to know if the person can themselves use it. In the lazy river they had a device to lower a person into the water. There was also a ramp to the kids jungle gym portion and I did see staff pushing around a wheelchair that could go in the water.

Yes

Yup

Yes but they have rules as to which ones are allowed. They need to be Coast Guard approved, I believe.