Do you understand what I mean?

What I mean is that understood by you?

Was what I mean understood by you?

Is what I mean understood by you?

What I mean is understood by you?

All of the above

This is an interrogative sentence of Present Indefinite Tense.

Present Indefinite Tense

Active Voice: Subject + Verb + Object

Passive Voice: Object + is/am/are+ third form of a verb + by + subject.