are frogs nocturnel?

Answer 1

yes, some are. the reason is that most frogs (toads are dry terrestial kinds) are aquatic or amphibian, they can breath thru their skin, their skin needds to be moist, they gain and loose water thru their skin.
So in areas where sun and environment is too dry and hot (amphibians can't control their own body heat) for them they are active at night. Thus you hear the frogs at night in most parts of the USA. In other places like rainforests, under the canopy of tall trees this is not necessary for them. Also in places like Oregon Washington and Hawaii there is enough moisture on the ground and in the air they can live at any time of day. But they need to avoid direct sunlight if that would make them overheated.

Answer 2

Some are some aren't. Green tree frogs at my place are certainly nocturnal. There is a frog-eating bat that lives from Mexico to northern South America that locates frogs by their call and then catches them. The bats are nocturnal and so are the frogs they eat.

Answer 3

no they are up during the day time.

Answer 4

No