Im pretty dam old so I can remember 20 years ago and bitcoin would work still. We arent going to reset that far unless its a full nuclear war then it'll be 1914.
The difficulty would be much slower but they had Pentium cpu back then and parallel processing. Not that far off peer to peer and seti joint processing of packets and so on
3.) It's not accepted anywhere as money
4.) Verifying its authenticity is a hassle
Nope, your off the rails there. Its accepted many places, used as money for housing and large purchases maybe. Not in the West because we finance everything with debt. The real drawback maybe is negotiating a price but then you cant say bitcoin has an established price yet either.
The 'spread' is very large like you say, gold is a physical lumpy thing and theres personal security issues. This is bitcoin needs to shine, sleek, slick, fast and secure. It really needs to be click of the fingers easy to use because if they dont make btc as simple as email or text messaging then the banks will turn mobiles into ATM and they are not far off that now.
I can tap my card on a till and pay a bill in a few seconds, can btc do that anywhere even in theory. Thing is if dollar goes down, theres plenty others and people can just use VISA and canuck dollars instead. So gold is some backing to the normal banking system, many central banks do hold it and are buying more even and some like USA or europe are vastly negligent in their reserves and budgeting but the extreme is bitcoin which has no reserves of any kind and so it really needs to be king of transactional velocity and worth. Still a way to go
4.) Verifying its authenticity is a hassle
No its quite simple. Can it be done as simply as bitcoin, or cash actually yes if its in coin form. Gold has a fixed weight and a coin fixed dimensions so you have two elements of the equation to prove absolutely you have your gold there. What they used to do (obviously we stopped using coins of actual worth) is use fixed scales. So you put a gold coin into a set trap, it will only fit this coin regulated dimensions and then it has to equal perfectly the weight. Gold is a unique element so its really not possible to fake both weight and dimensions, so this quick test works and yes gold has worth as a transactional secure monetary thing!