I really wonder, though.
If we install the v0.1.0 in two computers and let them connect through the
GetMyExternalIP,
assuming “72.233.89.199:80” or any other IP they decide works, will they start mining the chain from the genesis block? Is there anything that'd prevent them from having their own chain since they'd not be interacted with the current nodes even if they connected somehow?
Well yes, but you might want to look into
testnet instead or as well as that - I think the download is quite a bit smaller too but that's a public chain.
I think there's a version around 8.8 or 12 that is compatible with the most recent blockchain
You're talking about Bitcoin-qt 0.8.0
I feel like there was one immediately after 0.8.0 that also had a major update - not sure how critical the memory leaks were of 0.8.5
I also think the original (0.1.0) version used a public key for identifying who funds were being sent to (making it much bigger than just using a hash of the key)
To be specific, it's uncompressed public key which barely used these days.
As well as the ripemd160 hash that also gets used which probably means the address is quite a lot smaller than an uncompressed public key.
I think there was a pay to IP option at some point too that got removed (it had quite a lot of problems associated with it - especially since communcations weren't encrypted).