Claims that would be covered under a HO3 and not covered HO2?

I understand about named Peril and Open Perils. However, I need examples of covered situations on an HO3 that aren't covered on HO2.

One example of an HO2 claim that would not be covered under an HO-2 would be any water damage relating to water backup, foundation, or slow leaks. As you mentioned, the HO-2 is a named peril policy. The HO-2 covers 16 perils which are: fire, lightning, wind, hail, explosion, riot/civil commotion, aircraft, vehicles, smoke, theft, vandalism/malicious mischief, glass breakage, pipe freezing, volcanic eruption, falling objects, weight of ice, sleet, snow collapse, and electric current.  Although the 16 perils cover about 90% of all claims, the broadest and best coverage can't be found with the HO-2 home insurance policy. An HO-2 policy puts The burden of proof is yours to prove that your loss was caused by one of the named perils. The HO-3, on the other hand, is what is called an "open" perils policy. Everything is covered except what is specifically excluded. For example - earth movement, flood, nuclear hazard, and war are excluded. That means the burden of proof shifts to the company to show that your loss is not covered because it was specifically excluded. The default position is you are covered. Here is more information on homeowners insurance. Good luck and if you have any other questions, don't hesitate to ask.