When using Continuous Scroll you can lock the screens so that a learner needs to interact with content before they can proceed. You can prevent scrolling by setting screen level Display Conditions on each of the screens. Here's how;

1. Ensure your topic has been set to Continuous Scroll

2. Select the Display Conditions option in the properties field for Screen 2 

3. Add a Screen Status display condition so that it will only display once Screen 1 is complete (fully interacted with)

4. You can also set the Hidden Screens feature to be ON in the Theme settings for the course. This will display an icon indicating that Screen 2 is locked.

5. Once the Learner interacts with Screen 1 it will unlock Screen 2. Until the learner completes the interactions on Screen 1 they will not be able to scroll down the screen. This process can be repeated for each screen in the topic