Your friend is correct. "Reply" is typically an intransitive verb, which means it does not take a direct object. "Tell", by contrast, is a transitive verb, which does take a direct object. So:
Please reply him. (Incorrect)
Please reply to him. (Correct)
Please tell him. (Correct)
It doesn't matter whether the subject is a person you're replying to or an email you're replying about - the rule is the same.
Please reply his email. (Incorrect)
Please reply to his email. (Correct)
M-W Dictionary shows that you can also use "reply" as a transitive verb, but that's a more specialized use such as you would see in dialogue:
"I'd like some water please," she replied.
The Original Poster's four examples are all grammatical. However, the sentences with there are preferable in most situations. The reason is that the phrases a car and three cars are indefinite. A car uses the indefinite article a, not the. The phrase three cars doesn't use the word the, as in the three cars. It's also therefore indefinite. This means that we haven't been speaking about the car or the three cars before.
In English we don't like to use indefinite noun phrases as Subjects. We like to put old information, stuff that we have already talked about, at the beginning of the sentence. If we put indefinite noun phrases at the beginning of the sentence, the sentence is more difficult for listeners to process.
If a sentence uses the verb BE, we can avoid this problem by using an existential sentence. We can use there is or there are. This moves the new information to later in the sentence where it is easier for the listener to process. Look at the following groups of sentences:
- A cafe is on the corner.
- A riot was in the West End.
- An accident was on the motorway.
- A meeting is at 2 o'clock in the main hall.
- A God is in heaven.
The sentences above are all grammatical, but they are strange and awkward. There may be some special time when want to say these sentences like this, but usually they are not a natural way of phrasing the sentence. If you generally speak like this, people will find it difficult to understand you, and they will know that your English is not very good.
If we use an existential construction instead (there is or there are), the sentences become completely natural:
- There's a cafe on the corner.
- There was a riot in the West End.
- There was an accident on the motorway.
- There is a meeting at 2 o'clock in the main hall.
- There's a God in heaven.
Notice that the problem in the first group of sentences is that we used indefinite noun phrases. If we use definite noun phrases, the sentences become completely natural. Look at these versions of the sentences:
- The cafe is on the corner.
- The riot was in the West End.
- The accident was on the motorway.
- The meeting is at 2 o'clock in the main hall.
- God is in heaven.
Those sentences sound like native-speaker sentences.
Conclusion
All four sentences are grammatically well-formed. However, the sentences with there are more natural, and will make you sound like a better English speaker. They will also make it easier for the person listening to you.
Best Answer
Well, your assertions are not entirely correct. For example it's fine to say
Use "about" when you want to know the general facts around some information, or when the direct and indirect object of the verb might not be clear. Example:
In the first example, the computer is the indirect object, from which he expects an answer. In the second it's the direct object, the subject of his query.
In the same way, it would be wrong to say something like, "He asked my mother's health," because that makes no sense. You can't ask anything of someone's health. Instead say:
Because adding "about" can imply that the information is doubtful or unusual, don't use it when requesting specific, well-defined information such as, "The doctor asked my date of birth." Instead use it when you want to know more peripheral detail:
In some situations, however, "about" implies courtesy, as indirect questions may be more polite in certain contexts.
Note there are many other ways to express this kind of polite deference: