Bike frames aren't very tightly controlled. In something like flyrods, enormously tight controls for stiffness are used. Even with those heat treating is sorta at the marginal end of the spectrum of distinctions. So with the kind of construction where tolerances aren't even being held to the 1/10" heat treating isn't something you should loose a lot of sleep over. On the other hand it can make the grass a nice dark colour.
England, currently dividing my time between university in Guildford and home just outside Reading
Too many to list here!
How long do I have to let the bamboo age, and should I age it indoors or out? Also, should I go for steel dropouts, bb, headtube etc or aluminium ones, in terms of how easy they are to bond to the bamboo?
You don't need to age it, it will be dry by the time it gets here. The bamboo goes through quite a trial by fire in being brought to market, they cook it and straighten it. It may also have taken on some water due to how it has been stored on the way, but just like buying wood, you assess that stuff when you get it here.
Aluminum probably plays better with epoxy, and it weighs less so why use anything else.