The difference is, people in stone age had no idea what nuclear fission means. They might have believed you, albeit superstitiously, if you told them that there will be food everywhere one day.

Interestingly, the examples you cite seem to be in a decreasing order of difficulty, with several orders of magnitude more of effort required. AGI is gonna be much easier than living forever, which seems should be easier than travelling faster than light.

ISTM that AGI would swiftly result in vastly extended lifespans, at least for those fortunate enough to be at the control knobs. In that sense, they are at the same difficulty level.