Really, the verb that makes sense in the context of rain is "to fall." Rain does not really descend or ascend.
Descend is a downward movement and is just fine. While "fall" is more common, "descend" is also used in reference to rain. It's perfectly acceptable.
In English rain or rains do not descend, they fall.
Descend is also used. It's fine.
Why is "The rains fall from the sky not accepted"? This is a more natural English sentence and contains the same idea of moving from higher to lower level.
Is heaven instead sky acceptable
It should be. However, "rains" makes no sense in that context.
Latin "de" more closely translates to "down from", so "Rains descend down from the sky" should be accepted, along with "down from" every other time "de" is used.
Descend already means down. Adding the word down is a redundency, and not appropriate.
the rains drop from the sky. why is my answer wrong?
Because descend does not mean drop. Two words, two different meanings.
And we have a perfect exact word to translate it to.