Question on the Japanese language?

You would still add か. It works in all situations, even with question words.

どうしてそんなことをやりましたか。 (Doushite sonna koto wo yarimashitaka.) Why did you do such a thing?

これは何ですか。 (Kore wa nan desu ka.) What is this?

この漢字はどうやって書きますか。　(Kono kanji wa douyatte kakimasuka.) How do you write this kanji?

一番近いコンビニはどこですか。　(Ichiban chikai konbini wa doko desu ka.) Where is the nearest convenience store?

終電はいつ出発しますか。　(Shuuden wa itsu shuppatsu shimasuka.) When does the last train depart?

Note that か can be omitted in informal speech. Informal questions don't always include か but are instead made into questions with rising intonation and/or other particles, such as の, but you don't have to think about those yet :)

I hope you found this helpful!

Yes, you are right with your assumptions. You need ka to make it a question. If you want to ask, what kind of cat it is, you can say, "sore ha dono you na neko ka". Ni turns to na, because "dono you" is treated as an adjective that determines neko.