What have you eaten Is it correct?

“What have you eat” is not a correct English. It should be “have you eaten”. There’s no significant difference between those examples, just the p. perfect version(have you eaten) is more common is BrE, and simple past(did you eat) is more common in AmE.

Have you eaten meaning?

The person is basically asking you whether you already had your dinner/lunch/breakfast. Sometimes, it is an indication that they want to invite you out. Sometimes, it is an indication that they worry about you. Sometimes, it is just an indication to know what you ate that time.

Is it I have eaten or I had eaten?

What else would you eat? I would say “I have eaten” or “I had eaten.” Both are correct. The difference is that “had eaten” is past; “have eaten” means you ate recently.