to change constant.

Although the meanings of words may necessarily be liable to change constant.

Is this sentence correct?

No. Probably it was supposed to say “liable to constant change” or “liable to change constantly”, but “necessarily” doesn’t seem to fit either, and, in any case, it is not a complete sentence: “although” requires some contrasting clause to be present.

Although the meanings of words may necessarily be liable to change, it does not follow that the lexicographer is therefore unable to render spelling, in a great measure, constant.
What about now?

Yes, that looks OK.

Is the sentence I write in my first post core sentence of the sentence that I write in my second sentence?

That’s okay grammatically, but the idea it conveys through the use of ‘although’ sounds odd to me.
It is saying
Despite the fact that word meanings might change over time, this does not indicate that experts can say spelling stays the same.

Are you the same poster as “Reading Comprehension” then?

The word “constant” applies to “spelling”. It does not have any connection with the first clause about meanings of words being liable to change.

I don’t think it means that, Beeesneees. Did you accidentally miss out a negative?

yes

Oops, yes.
Thanks.
… experts can not say that…