Reset, - No, not if you have no code.
To silence it, pending expert help,
Firstly isolate the mains supply to it. This is probably a fused spur somewhere near the panel. Don't go any further until you have done this!
Secondly, remove the cover panel and pull one of the push-on connectors off the battery. That should silence internal sounders.
An external box may continue, but not for very long, say 30 minutes max, as it has a small internal battery.
To re-commission it you need two codes, the user code, and the engineer code, and will probably need expert assistance. It may even be impossible with some models.