によらず

によらず means "regardless of": what the sentence says holds whatever the noun turns out to be. It follows a noun directly. It is the negative of よる, "to depend on", in written style, so the literal sense is "not depending on ~".

It is formal and belongs in rules, notices and job adverts. In conversation you'd say かんけいなく関係なく: ねんれい年齢にかんけいなく関係なく.

いかんによらず

いかん means "how it stands", so [noun] + の + いかんによらず is "however the ~ turns out". It is stiffer still, and turns up in terms and conditions.

によらず, にかかわらず and を問わず

All three translate as "regardless of", and in a notice they mostly swap freely. によらず keeps the sense of よる: the noun is not what the decision rests on. をとわ問わず says the noun isn't asked about, and suits pairs like だんじょ男女. にかかわらず goes after a clause as well as a noun: いく行くかいかない行かないかにかかわらず.

見かけによらず

One fixed phrase is common in everyday speech: 見かけによらず, "contrary to how they look". The proverb 人は見かけによらない ends on the plain negative.