Significantly less time if they simply “acquire” the information needed via industrial espionage :)
EUV is the way that won from the R&D by the current leaders.
It might not be the only way to get things to work, though clearly I have no real idea. :)
Not with $140B in a country where literally everything is cheaper, and not when they know it can be done (and likely also have at least half the technical documentation). It won’t take a “decade”.
Apparently they're working on a DUV 3nm process, which is a little insane if you think about it. Would certainly be interesting to see it working, if it does work.