How can I know which version you want?

Hola Kay

I had a look at all test-questions for this topic to see if there was any ambiguity, but all these questions are set to choose one option from the dropdown menu. There is only one possible correct answer on each of them, so all the others are not answers that could be possible for "the other you", meaning that it leaves you with one possible correct answer each time. If you chose another of those incorrect answers, they are all incorrect for any type of "you".

If there is a test-question where you have to type the answer, then you'll always find a clarifification on the HINT, and in this case it would be saying something like "you refers to you singular informal", or "you refers to you plural formal", for example.

I hope this clarified it.

Saludos

Hola No

That question is giving you the clue right at the beginning with the "¿Te... " which can only mean "Do you (singular) like...?" If we were referring to a plural you, it would either start with "¿Os...?" for Peninsular Spanish as in "vosotros", or "¿Les... ? if it was referring to "ustedes". 

Independently of who does the liking, the thing is you don't really need to know that because the verb is going to be either gusta or gustan; it would be gusta if what is liked is one thing, and it would be gustan if what is liked is something plural. 

Look how the verb changes depending on what comes after (never mind who likes it):

¿Te gusta el café?

Do you (singular) like coffee?

¿Te gustan las manzanas?

Do you (singular) like apples?

¿Te gusta la playa?

Do you (singular) like the beach?

¿Te gustan las películas románticas?

Do you (singular) like romantic movies?

If we change it to another person doing the liking:

¿Les gusta el café?

Do you (plural formal) like coffee?

¿Les gustan las manzanas?

Do you (plural formal) like apples?

¿Os gusta el café?

Do you (plural informal) like coffee?

¿Os gustan las manzanas?

Do you (plural informal) like apples?

I hope this clarified it.

Saludos