Learn Italian: In quale gioco si torna indietro sul tabellone? - In which game does one go backward on the game board?

Quale is an interrogative adjective meaning 'which' used to ask about a choice among options. It must agree in number with the noun it describes. Because gioco (game) is singular, we use the singular quale. If you were asking 'in which games', you would use the plural: In quali giochi.

What is the si doing in si torna?

This is the impersonal si. It is used when you are talking about people in general rather than a specific person. In English, it translates to 'one goes', 'you go', or 'people go'. So si torna indietro means 'one goes backward' or 'you go backward'.

I know su means 'on'. Why is it written as sul?

In Italian, when the preposition su (on) is followed by a definite article like il (the), they must combine into a single word, called an articulated preposition. Su plus il becomes sul. Therefore, sul tabellone means 'on the board'.

Why does the sentence use torna for 'goes'? Doesn't it mean 'returns'?

Yes, tornare primarily means 'to return' or 'to come back'. When paired with the adverb indietro (backward), the phrase tornare indietro literally means 'to return backward', which is how Italians express 'going backward' or 'moving back' on a game board or in real life.