The answer "he likes pig" is not natural. It could be accepted, but "he likes pork" is more natural in English.
So yá' át' ééh can mean hello, good and also to like, without any conjugation?
Yes. Basically it is, "with him, it is good". If you want to say "I like this" it is "shił yá'át'ééh", literally "with me it is good".