Anonymous“"Open the door"”
That is an imperative sentence. We don't usually change imperative sentences to the passive form. In your imperative sentence, it is clear that the speaker is telling "you" to open the door -- even though the word "you" is not used in the sentence. Trying to use a passive form would remove the clear idea of "you" -- which is the whole point of using an imperative sentence in the first place.
You could say something such as this:
- The door must be opened.
OR
- The door is to be opened immediately.
However, the idea that "you" (rather than someone else) are the one who should open the door is lost in those passive sentences. So, neither one is really a good transformation of the original imperative sentence.