If I am engineering a first iteration of a project, I can say, "I am making my prototype", or, "I am prototyping".
The "Proto-" prefix means "first, foremost, earliest form of," according to Dictionary.com, but I don't see a prefix meaning "second, second form of" or anything similar in meaning.
I am merely curious in the possibilities of a "second", because if there's a first, there is hope for a second.
Short answer, you can't make up words by switching a prefix, and be reliably understood.
Even shorter answer, the prefix is "deutero-"
But the most common word which uses it is "Deuteronomy" (the second knowledge or the second telling of the law in the Bible, one of the books of the Torah) And that is not a common word! Other examples are far more obscure: such as deuterostome (a division of life in which the embryo develops a mouth second after the formation of an anus).
There's no standard word "deuterotype".
Although the etymology of 'prototype' does mean the first preliminary version of something, in practical use you can have first prototype, second prototype etc. These models may be numbered P1, P2 etc while in development.
Between prototype stages and the production model of something, there may also be a pre-production model (or multiple models). Each manufacturing industry may well have their own terminology so there may not be a single correct answer here.
The field of software development tends to use the terms alpha for the initial internal-only versions of a product, beta for a more developed version that may go out to a small audience for testing, and a release candidate for a successfully-tested beta version that could go into production. You may find these terms in use in some manufacturing industries, too.
Deuto.
Seems to be used only in Chemistry.
https://www.oed.com/search/advanced/Entries?q=deuto&sortOption=Frequency
deuto-, comb. form In Chemistry to distinguish the second in order of the terms of any series. Thus deut-iodide, deuto-bromide, deuto-carbonate, deuto-chloride…
