Presentation remote on your phone: clicker for slides

No. A web page can send key presses only to itself: they reach neither another application nor even the next tab, and remotes that promise to control PowerPoint require installing a program on the computer. Here the deck opens on this page instead: save the presentation as a PDF and open it together with the PPTX, so the slides come from the PDF and the notes from the PPTX.

Click “Projector” in the bar under the slide, and a separate window with the slideshow opens. Drag it to the projector (in Chrome and Edge it goes there by itself if the browser is allowed to see your screens) and double-click to make it full screen. The laptop keeps the next slide, the notes and the timer, and the phone still changes the slides.

The slideshow won't stop: the deck is open on the computer, and you can move through it with the arrow keys or a clicker. When the link drops, the phone shows “reconnecting” and connects again on its own, taking the slide number from the slideshow, so it never falls out of step with the screen. Even a page reload on the laptop doesn't mean scanning the code again.

Yes. A clicker sends PageDown and PageUp, sometimes the arrow keys, and “B” or a period for a black screen, and the slideshow understands all of these. A slide number followed by Enter jumps to that slide, as in PowerPoint. You can use the phone and the clicker at the same time.

Because the slideshow sends the time already elapsed rather than the moment it started, and the phone keeps counting from that value on its own clock from the moment it arrives. Phone and laptop clocks often differ by seconds, and by minutes if they aren't synchronized; counting from the other device's start time would be off by exactly that difference.

Yes, for this deck in this browser: open the same file again and the notes return to their slides. A different deck or another computer won't see them; for that, keep your notes in the PPTX and add it together with the PDF.