Interrogative words ask information questions (not yes/no)
"Quand" and "à quelle heure" are not interchangeable. Use "Quand" to talk about a day or a date, and "à quelle heure" to talk about a particular time of day.
Remember: You can use "est-ce que", "inversion" or put the question word after the verb.
Est-ce que: Comment est-ce que tu t'appelles?
Inversion: Comment t'appelles-tu?
After the verb: Tu t'appelles comment?
It's impolite to use "Quoi" if you don't understand what's being said. Use "Comment?" or "Pardon?" instead
"Quel" is an adjective, so it needs to agree with number/gender with whatever it modifies.
masculine: quel hôpital?
feminine: quelle place?
masculine plural: quels restaurants?
feminine plural: quelles montagnes?