can't wait

[John]

Are these all OK and natural?

1. I can't wait to know the answer to the riddle.
2. I can't wait for the answer to the riddle.
3. I have an itch to know the answer to the riddle.
4. I have an itch for the answer to the riddle.
5. I'm impatient/desperate/crazy/mad/dying/itching to know the answer to the riddle.
6. I'm impatient/desperate/crazy/mad/dying/itching for the answer to the riddle. [These are a little unnatural, isn't it?]

Thanks.

[Rusty]

Are these all OK and natural?

1. I can't wait to know the answer to the riddle.
2. I can't wait for the answer to the riddle.
3. I have an itch to know the answer to the riddle.
4. I have an itch for the answer to the riddle.
5. I'm impatient/desperate/crazy/mad/dying/itching to know the answer to the riddle.
6. I'm impatient/desperate/crazy/mad/dying/itching for the answer to the riddle. [These are a little unnatural, isn't it?]

Thanks.

1. I can't wait to know the answer to the riddle. (OK).
2. I can't wait for the answer to the riddle. (OK).
3. I have an itch to know the answer to the riddle. (OK, but unusual).
4. I have an itch for the answer to the riddle. (Unnaturall).
5. I'm impatient/desperate/<strike>crazy/mad/</strike>dying/itching to know the answer to the riddle.
6. I'm impatient/desperate/<strike>crazy/mad/</strike>dying/itching for the answer to the riddle. [These are a little unnatural, <strike>isn't it</strike> aren't they?] (I'd say that "desperate" is a bit unlikely. "I'm dying for the answer" and "I'm dying to know the answer" are both common).