Only the first is both natural and correct. The second is possible in some contexts, though people don't normally 'need' to help with things. The third is wrong.
1. What do you need help with?
2. What do you need to help with?
3. What need you help with?
Are these sentences all grammatical and same in meaning?
Only the first is both natural and correct. The second is possible in some contexts, though people don't normally 'need' to help with things. The third is wrong.
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Even if #2 were natural, it wouldn't have the same meaning as #1.