Here are the answers to your questions:
-
When it’s not an inversion question or est-ce que question, what is it?
- Answer: il y a question
-
What’s the conjugation of the verb avoir at the third plural subject?
- Answer: ont
-
What’s different if we use combien before the verb coûter?
- Answer: The preposition de disappears.
-
What is the translation of how much?
- Answer: combien
-
What’s the letter we put between a and il in the inversion question?
- Answer: t
Feel free to ask if you need further explanations or additional questions!