This sentence is not grammatically correct

amigueo:hi, this is about english and about esperanto.

"i will eat the cake when you make it", ok, that is the meaning, but...

"i will eat the cake you have made when". is this a correct sentence in english?

"mi manĝos la kukon kiam vi faros ĝin aŭ kiam farita de vi", mi ne scias ĉu esperanto permesas pli anglecan esprimmanieron

"I will eat the cake when you make it" - This is perfect.

"I will eat the cake you have made when." - An incomplete sentence. "I will eat the cake you have made" is a complete sentence, so by adding "when", you are starting a new clause, which you then do not finish. In the first example, "I will eat the cake" is a complete sentence, but you added the clause "when you make it", which is fine because you finished the clause.

"Mi manĝos la kukon kiam vi faros ĝin" - this is a complete sentence just like in english.

"Mi manĝos la kukon kiam farita de vi" - we don't know which object is "farita" - are you eating the cake when the cake is done or are you eating the cake when you are done? That makes this sentence unclear, so it should be avoided.

Altebrilas:Is it possible, to the interrogative form?

Baker: You will eat the cake I make when... [inaudible, e.g. ...you can afford it]
Boy: I will eat the cake you make when?

It would be written as "I will eat the cake you make when...?" because you are prompting a response. You are essentially repeating what you heard the other person say so that they can repeat the rest of what they said. It's not actually a sentence itself (and also not considered a very polite way to go about asking them to repeat what they said - it's not exactly rude, but it's very casual). If you wanted to ask what the rest of the sentence was, you could say "Sorry, what did you say?" or "When will I eat the cake?" - which are fine in both polite and casual circumstances.