Can I fit into a size 12 snowboarding boot?

Probably.....it depends on the shape of your foot and how used the included boots are. There is a memory foam in most boots that packs out relatively quickly, and if its shaped to someone else's foot it will make yours hurt. I would almost say, sure buy this package deal, but then hawk the boots and buy brand new ones so that they are shaped to your foot and you know they are comfortable and have an optimal fit. Sacrificing on boots is not something you want to do when shopping for gear.

There is no way to answer this as there is no consistency in boot sizing from one brand to another. ...and often even within brands. Most major companies have their boots produced in factories in one or more foreign countries. This being the case, most of the US sizes that boots are labeled with, are actually approximated conversions from one of five foreign sizing standards. To further exaggerate the problem, the companies use different lasts (templates around which the boots are created) which also vary in size. For a rough idea of how foot measurement should relate to shoe size, and how the many international sizing standards relate to each other see our site for a chart. Also, used boots will already be packed out to the original rider's foot, so that will affect sizing.

Yeah, that should work. See if you can try that boot on at a boardshop or something.