Colecanth don't you realise that questioning others' beliefs is like promoting yours. what answer you are expecting for your questions: Will God ask for your religion when you die or Did God put Quran in Prophet's mouth, etc..

What muslims believe is that the first qestion above is one among the three questions that the angel of God asks when a person is buried and woken up in the grave.
The second one is quite obvious that even a non muslim understands what muslims believe of Quran, a word of God delivered to Prophet Muhammed. This is keeping with the Book..

Now what reason would I use to justify these? Even if I did attempt, would it be of any convincing for you?

The only possible conclusion is that there is no proof. Isn't it?
Is it a rocket science for you to understand this simple fact that you go on putting this questions to believers?

Now what action you are going to take.