Taking the easy answer first - the 72-500 is certified (since 2011) for operation on unpaved runways, by EASA (European, but the application was for using one in Papua New Guinea). Landing distance on pavement is exactly 3,500 feet (no room for error) and MTOW take-off distance on a paved runway requires 4,265 feet. Gravel runway would produce more drag and require a longer TO roll.
So not likely, except at very low weights.
Certification - I can't find a document, but it is probably certified in general. However the plane is prone to icing issues - see:
American Eagle Flight 4184 - Wikipedia, the free encyclopedia
Aero Caribbean Flight 883 - Wikipedia, the free encyclopedia
.....and American Airlines quit using them even in the northern US, let alone Canada. Moved them all to southern/Caribbean routes. Most operators today are in subtropical or tropical areas, or freight companies.
On the flip side, they are used by Flybe Nordic/Finland out of Helsinki, so not totally absent from cooler climates.
Given that the competing Bombardier Q-400 is a homegrown Canadian product, the ATR is/was likely a hard sell in Canada even without its icing issues.