Gold could be used during the medieval ages as a form of payment - today it can't - in the future it can't.
I think it can, and the probabilities to that is big, have you ever wondered why every country in this world is stacking gold?
Imo Bitcoin (blockchain) combined with Gold is really the future currency. Gold have difficulty in term of big transaction (need space and time to transfer it) but blockchain answer it. Bitcoin have problem with trust (cause mostly people want have wealth that they can touch, see and keep) gold answer it. So i think bitcoin (blockchain) and gold can stand side by side as strong currency (blockchain as a system and gold/percious metals as medium)
It's so easy to make fake looking Gold, that it would be impossible for the public to determine if it was real or not.
im not sure with that, cause testing fake gold or not is easy, just use magnet or even just bite the gold. but if you want perfect result use nictric acid.
If the entire world went into massive crisis, with no internet, no fuel, shortage of food etc, I bet you that food/medicine will be the primary currency. I will trade you 2tons of gold for 1kg of food because my family is starving.
when that happen food/medicine/gold still will be a goods. At that time, yes food/medicine have more value rather than gold but also they have limitation which is age, so imo they can't act as primary currency cause of their limitation.