analysis
I don’t know what the truth is.
S:I
V:know
O:what the truth is
I have no idea what the truth is.
S: ?
V: ?
O: ?
Which one(s) is/are correct?
I have no idea [color=red]about it.
I have no idea it.
I have no idea what the truth is.
I have no idea [color=red]about what the truth is.
Thanks.
We’re not doing your homework for you,
Please, post your ideas first 
Ohh, it’s not my homework, I’m not that kind of a kid, who doesn’t want to do the work. 
What I ask are the things I haven’t understood clearly in school. I’m not that kind of teen really.
My thought is that: I can easily point out that ‘I’ is the [color=darkred]subject, ‘know’ is the [color=darkred]verb, and ‘what to do’ is the [color=darkred]object of the verb ‘know’.
“I don’t know what to do.”
Yet I don’t understand where the object is, and what is the object of.
“I have no idea what to do.”
I know the subject is ‘I’
the verb is ‘have’
the object is ‘idea’
[color=red]then what about ‘what to do’ what is it??
'.
I - S
have - v
no idea - O
what to do - Object complement
.
One more, need prep ‘about’?
Which one(s) is/are correct?
I have no idea about it.
I have no idea it.
I have no idea what the truth is.
I have no idea about what the truth is.
.
These are OK:
I have no idea about it.
I have no idea what the truth is.
I have no idea about what the truth is.
.
Thank Mister Micawber.