I would concur, a principle(s) precede ethics.
I would not consider a principle a concept, rather I would consider a principle a proposition.
I would apply 'valid' or 'invalid' to concepts.
I would apply 'true' or 'false' to principles.
The three Objectivist primary axioms are tautologies, converting them essentially into axiomatic principles.
All truths depend on the validity/invalidity of the concepts involved which invoke said principle.
As to fundamental, primary or general truths: I tend to hold that to the propositions as asserted; i.e.; are the propositions true based on the validity of the concepts invoked to assert them.