Mistake/mistakes (question)

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Feb 11, 2012 11:03 grammar plural
Do you think which sentence is correct when I ask for the correction on my Lang-8 entries?
1."Is there a mistake?"
2."Is there any mistake?"
3."Is there any mistakes?"
4."Are there any mistakes?"

I think the third sentence is incorrect because the verb is singluar while the noun is plural. Also, I think No.1 and 4 are both correct. I think that if a person thinks there is no mistake in his/her writing, he/she tends to say the first sentence and if he/she isn't really sure whether there are mistakes or not, then the person tend to use the fourth sentence.

Is my understanding correct? The more carefully I try to look into small differences, the more confused I get.