nix, or nixpkgs, does not really have a concept of multiple extant versions of a package. i see this worked around in cases of overwhelming importance with e.g. python312, python313 etc.

but in general if you need an older version of package XYZ you are dealing with a git history search and pinning to a commit

there is no fundamental reason why nixpkgs HEAD could not contain the logic for multiple versions of package XYZ

so - to start from the beginning - is there something in nix itself that keeps me from e.g. writing opentofu-1.6.3 or opentofu==1.6.3 or whatever as the package i want to install?

background: i want to introduce nix devshells in a company where this kind of situation happens all the time (i.e. some project has to be checked out from github and worked on using a list of software versions that is both brittle and not recent)