Is NH4OH a solid

Answer 1

NO. NH4OH is formed when Ammonia Gas (NH3) combines with water in solution :

NH3(g) + H2O(l) <=> NH4OH(aq)

There is no solid form in the normal environment. When the solution reaches saturation, NH3 will begin to offgas until equillibrium is reached.

This is true for the "normal" world of chemistry. I have no idea whether exotic environments could be created where NH4OH would crystalize, but it will not in your home lab.

experiment: pour a shot of unscented household ammonia (NH4OH) into a cup and leave it out until the liquid has evaporated. Or boil it in an appropriate vessel (Don't use aluminum)