"Israel" and "Ephraim" are terms used to speak about the people of the northern kingdom. Samaria was the capital of the northern kingdom. (See: [[rc://en/ta/man/translate/translate-names]])
This chapter makes it clear that the northern kingdom is going to be nearly decimated as a people. They will no longer exist as a nation.
Hosea uses rhetorical questions throughout this chapter. They are not questions requesting information but rather questions indicating some emotion like anger or dissatisfaction. (See: [[rc://en/ta/man/translate/figs-rquestion]])