You will get a shock and surprise. Grocery Challenge project they have created and expecting the developer to fill in blanks with production-level code and that too in 30 mins, is crazy, dropping UI elements on story board with auto layout only take some 10-15 mins. In rest 15 mins what a developer can write at the most? Think if you want to write protocols, a different data source class, invoking a network API, writing a collection view cell class to bind data received from the network API.
They want you to create a screen with a Question label at the top and below it 4 grid images and at bottom a Submit button.
Data for Question label and images url comes from the server so you have to invoke a network api to get 1st Object of type Question , which has a array of type Answer Object, Answer object has field for imageURL. So once you get Question Object use answer array to load images. Answer object also has field called correct:Bool which tell whether this image is answer or not for that Question label.
Even if you use buttons like IBOutletCollections , 15 mins are not at all enough to complete what is asked all.
Very immature seems Instacart is not paying attention to this, either you should know this Grocery Challenge solved before even the test starts then you are good.