Practically all the elements heavier than lead are created by neutron capture in the r-process. This requires the explosive conditions of a supernova or neutron star merger.

In terms of some limit, I'm not sure how to answer. Stuff that's heavier than Uranium has a short half life compared to the age of the Earth, so there's not much to be found. They may have been produced in supernovae, but rapidly decayed.

We do know (at least theoretically) that much heavier elements were created indirectly by a supernova, in that they exist in the crust of a neutron star. Calculations show that atomic numbers of more than around 150 are possible at densities of a few $10^{15}$ kg/m$^3$, largely due to the suppression of beta decay by degenerate electrons.

Practically all the elements heavier than lead are created by neutron capture in the r-process. This requires the explosive conditions of a supernova or neutron star merger.

In terms of some limit, I'm not sure how to answer. Stuff that's heavier than Uranium has a short half life compared to the age of the Earth, so there's not much to be found. They may have been produced in supernovae, but rapidly decayed.

We do know (at least theoretically) that much heavier elements were created indirectly by a supernova, in that they exist in the crust of a neutron star. Calculations show that atomic masses of more than around 300 are possible at densities of a few $10^{16}$ kg/m$^3$, largely due to the suppression of beta decay by degenerate electrons.