There's 21 millions of Bitcoin and not any less or more. That's as simple as this, so no, it can't fluctuate.
yes that is a fact, the number of bitcoin is increasing by the minors but not decreasing, only the value of bitcoin can fluctuate and not the number of bitcoin.
Original amount of bitcoin nobody ever will produce, because a certain amount will still be lost and will not be available to the user. Such analyzes give predictions experts. But because of this price will not fluctuate.