Fish that have fins and scales
Observant Jews do not eat crayfish.
Jews who keep kosher don't eat fish wihout scales (Deuteronomy ch.14).
Yes.
yes they can
No, monk fish has been determined to be non-kosher.
At the time of the Mishna (200 CE), rabbis deemed it meritorious to eat fish on the Sabbath and Jews became accustomed to eating fish at festive meals. Gefilte fish, which has been called the quintessential Jewish food, is an especially popular fish to serve at the Passover Seder meal.
Fish and chips can be kosher if it`s made with kosher fish in a kosher kitchen. In fact, it was Portuguese Jews who introduced fried fish to England.
Moses and the Jews. Jonah and the fish.
Yes, religiously observant Jews can purchase fish from a store that sells non-kosher food. However, the fish in question must have its skin on. If it doesn't have its skin on, it must be in a sealed package that is labelled kosher by a reliable hechsher.
Gefilte
Gefilte fish is eaten on Sabbath and Festivals throughout the year. It has no specific relevance to Passover.