Regarding cloud ( if set to 0), is it that acquisition will not be planned if cloud is more that 0?

The cloud figure is a qualifier parameter, just that. The acquisition will not be planed if you have configured the sensor with a Cloud Constraint and the cloud figure is out of the defined bounds See more here:

There is an option provided for incidence angle for optical satellite also, is it applicable? what does stand OFF mean here

Yes, if incidence angle is defined for optical satellites, it will be used. You can define sensor geometries with three alternative methods: look angle, incidence angle, or Stand-Off Stand off is the on-ground distance between subsatellite point and observation point, measured at the equator. You can define the sensor geometry via Stand-off which is equivalent […]