You can still take a feat from your regular class at level 4, you don’t need to exclusively pick feats from your archetype once you have its dedication.

No. Feat from free archetype has to be from its dedication and it cannot be skill feat. And unless the GM says otherwise, normally level 4 dedication can't be taken with free archetype at level 2 or 4 (level 6 is possible since in certain dedication you can get 2 feat in level 4).