I want to start a wiki post about meta-result of meta-reductions in the theory of $\mathrm{NP}$-completeness.

This can be regarded as a reference request post. Any links are appreciated.

At least, this can be helpful in drastically mitigating the frequently asked questions related to homework assignments that are giving so much credit to @David Richerby, @D.W., @Yuval Filmus.