Is it a legal requirement to have a basic food hygiene to work with food?

It depends on the jurisdiction you are in.

You do NOT need a"basic food hygiene" [certificate] to e.g. replenish food stocks on a shelf in a supermarket, to sell prepackaged food behind a checkout till, to feed livestock/poultry, to pick fruit and vegetables for sale direct to the public or via a retail outlet or to work with food e.g. to offer to your family.