in refutation (resolution) can we use a clause that have been resolved

Question

In resolution if we have a set S composed of three clause C1, C2 and C3 and we want to proof that C4 is derivable from S using refutation:

suppose we've resolved C1 and C2 to C5, can we resolve C1 with C5 or C3 or C4 or C2 cause even it has been resolved?

and if we want to conceive an algorithm for that do we have to delete each resolved couple of clauses from or initial set I= {S, ¬C4} and add the resolvent instead?

and lastly, do we have to use all the clause to derive ⊥ or we stop once we find ⊥ even if we find it in the first step?

thank you for claryfing things.