For the most part, yes. Some things are hard to emulate, Weak References, E4X which is still wildly used, AS3 Namespaces, and all the graphics APIs. Flash just has a very different rendering model that doesn't easily map to Canvas.

The hardest part about Flash is understanding how timeline animations interact with AS code: events, object construction order, for all versions of Flash. Shumway supports all SWF versions and the the three programming languages that are supported by the Flash player: AS1, AS2 and AS3.