1) Many existing networks, including the Qtum network were sold on ERC20 contracts (https://qtum.org) originally as an ICO method before moving to their own network where they trade the tokens for coins on the network. In that case, Qtum continues to issue new coins on a proof-of-stake basis. There's other examples out there, this is just one I'm familiar with.
If you can point to 90° drops on GDAX, I'd be interested to see them.
If you can point to 90° drops on GDAX, I'd be interested to see them.