What would a conlang created to be an alternate version of an already existing natural language be classified as?
For example, a version of English that could have been spoken in an alternate steampunk-era Victorian England, or a conlang of the Finnish language in the year 2349. To be clear, I'm assuming that the conlang would be an actual, dedicated one, and not just a few "alternate" words thrown in for flavor; the examples I picked were just the first ones that came to mind.
(Bonus: is there a classification for a conlang created to be a conlang of a conlang in this same way?)