I believe that your analysis is mistaken: to have in this expression is intransitive. You should work hard to make this assertion.

Why is the verb have transitive? Argumentatively, I would argue that to have at is a phrasal verb, whose object is syntactically the object of the preposition at. What do some other phrasal verbs mean for look at?

So to have in this idiom is intransitive, and the imaginary object is expressed as the object of the prepositional complement at.

Your options (A) and (D) are correct, while (B) and (C) are incorrect for the meaning you’re trying to convey.

If I asked people to do me a favor, they said no.

The word “would” here is correct idiomatic English. If you extract the if clause into its own sentence you get “They will do me a favor..’ When used as a subordinate clause with if, the verb will must become would in order to agree with the past tense asked.

I asked them if they did me a favor. And they have no answer.

What is its weirdness and ungrammatical? In both clauses the tenses should agree in most situations, and in any case no English speaker would ever say this.

I asked them if they would do me a favor.

Originally written in 1923, the passage makes little sense. The tenses between these clauses agree as they should, but having both clauses in the past tense means that you’re asking if they have already done a favor for you. What will you be saying if that is not what you want to say?

I asked them to do me a favor. They’ve done everything perfectly. I’m proud of them too. What will the characters like.

Is this semantically equivalent to the first option, but the syntax is completely different? Since infinitives have no tense, to do is correct here. This option is given if you are nervous about tense agreement and modal verbs.

It helps to keep time and reduces stress.

The construction If not for X is an idiomatic phrase in English. If verb to be is left out in this construction, though if you restore the full form which should always be: If it

were not for you, I would be poor.

If it’s true to say the original version without it

was wrong, it would be impoverished.

What is the meaning of the sentence if there are no you, and the verb if there are not you? The construction There is X cannot be used with a pronoun in place of X under most circumstances.

One sentence that my example sentence said “If not for you, who do I cook this cake for?” Is this a totally different construction, and the one in your question is even more unique?