@Mrinja According to the wiki, if a pumpkin crop grade drops to 0, it will die once it is fully grown. So if you plant a grade 1 seed, the crop will die if it has water neglect for two hours, but not if you keep it watered! If a grade 1 water neglected seed is without water for only an hour, it won’t die until that second hour. This also means that grade 0 seeds will die immediately once they reach maturity. So you technically can grow grade 0 seeds, but you won’t get anything out of it.

Dead crops and plants can’t be revived and are dead for good. The only thing you can do is destroy it. Dead pumpkins also can’t be harvested.
It says that pumpkins can only wither once they are full grown, and plants can only wither if they are in the “Ripe Product” phase.
And yes, that is a dead pumpkin crop!

There you go! I hope I explained it correctly!