Baking a Turkey takes around 15 to 20 minutes for each pound of the Turkey so for a 20 lb Turkey you would bake the Turkey for 300 to 400 minutes for the Turkey to be fully cooked.
A frozen Turkey can be baked however the frozen Turkey will take long to cook so it's best to thaw out the frozen turkey in your refrigerator for 4 days before it's time to bake the Turkey so that the Turkey will bake sooner.