No. Not compile on startup, but compile on background. This is what makes compilation time unimportant. If compilation is not available yet, then interpret it.
I know at least one Ethereum L2 who is already doing this and launched a testnet.
Yeah that’s an architectural limitation of Polkadot. However, this does not stop other chains from doing this, and they’ll be faster than Revive.
See Frontier’s optimization guide.
Right now we have been making a more comprehensive plan of Polkadot Compatibility Hub(s), and we’ll publish more details soon.