is there an observational test of verifying that we live in a FLRW-universe, i.e. of all (which?) symmetry assumptions behind choosing the Robertson-Walker-metric? is this a sufficient condition?
physics bonus question: can we test if the cosmological fluids are ideal?
maths bonus question: can you prove (by induction) the Bernoulli inequality, namely that
for all real numbers $x\geq-1$?