A question

Um. Do dated recipes count for the synth achievements?
And if so do they still hold their old recipe levels?
Like walnut mask 41+ still?

Any recipe counts towards the synth achievement, whether it be dated or not.

I'm not sure what you're asking about with the date walnut mask recipe — has it changed in the past update? — but as FFXIV-db and Mooglebox both list it as 41-50, then I would say it counts for 41+.

Yes.
Yes.
and yes.

Nice thanks peeps.
Walnut can be used in two stages then.