"Which do you like better, pork or beef?"
When the particle と is used as "and", it lists thing exhaustively, i.e. there is nothing else to consider. If you were to say 豚肉と牛肉が好き, it would mean "I like pork and beef." There is no implication that you might like anything else.
Another particle (don't worry if you don't know it yet), や, lists things inexhaustively, i.e. "Things like X and Y and ~ … " So, 豚肉や牛肉が好き would mean, "I like things like pork and beef." It implies that you like other things as well.
To summarise, と refers to/adds things to an exhaustive list. や refers to/adds things to an inexhaustive list.
I refuse to make this kind of choice. Just stick the pig inside the cow, the turkey inside the pig, the goose inside the turkey, the duck inside the goose, the chicken inside the duck, the fish inside the chicken, deep fry it all, slather it in barbecue sauce and call it a day.
Hi, the casual form of です is だ, you may know, or like you noted to omit completed. The more typical casual question marker and the one used in duolingo is not "か" but "の." Or to omit it entirely and have tone indicate that it is a question.
好き is a な adjective so you have a couple options for the casual. One, like we said, is to leave the ending off entirely and end with 好き? with the tone indicating a question. The other would be end it with なの.