I have a recipe for sweet corn bread and it calls for fresh corn and it is very hard to find fresh corn in winter; can it be replaced with frozen corn?
Personally I find frozen or canned is usually much better quality taste and texture wise to the fresh cobs. Good quality canned/frozen sweet corn is picked and frozen/canned within hours of picking whereas cobs in the market could easily be over a week old by the time you get it home.
So yes, you can easily substitute canned/frozen for fresh.
Same goes for peas.
Nothing like fresh, in season, corn. However, it freezes well and frozen corn is an acceptable substitute. You could also try canned corn, which would provide a corn punch, but may contain extra salt and/or sugar.