When an interrogative pronoun is the subject of a sentence, do is unimportant. As interrogative pronouns normally need to be at the start of the sentence, subject–verb inversion doesn’t happen either.

He makes cars that aren’t made of fuel because he makes cars. Who makes a car?
When the question does

not have an interrogative pronoun as the subject, ‘Do’ or another modal verb is required. What is the verb before its subject?

How do we make car? How? is an interrogative adverb. “Who is the subject/us”)

1. How to make a car is not a sentence; but it’s a subordinate clause. It’s certainly not a question.

2. How can I make a car a sentence and a question? I am not able to explain why i like car. However what should I do? What is your take on the word “Give”? Both

come from the structure We make a

• car in Indef_manner where Indef_manner

means some indefinite manner or way (of making a car).
The interrogative pronoun is what gets turned into how. In analogous situations, the word
Indef-manner often gets replaced with how.

The difference between the two examples that come from this structure is that
the first sentence has a pronoun in front, but no other change, while the
second sentence contains a pronoun in front, and an auxiliary verb before the subject.

How do you put a verb before the subject? The second question is still a question. How can this be explained?
The second one is an embedded question, or free relative, which is a type of complement clause.
Embedded questions invert verbs with the subject as shown above but invert auxiliary verbs in the subject.

• And why is this car so ugly?
  How can auxiliary verb precede subject these car ugly?
• 
  (embedded question object complement of know ; subject they preceded auxiliary verb can )