When login using user credentials given in the exercise : author_ui@gogoroad there is no option to switch between studios. There is no option to switch to DEV studio and do the exercise. Please check the issue and it would be helpful if same can be rectified today. Thank You.
The issue is that you're not in "editing mode". (In the bottom right corner of the screenshot, note the text that reads "Turn editing on".) It's possible that you accidentally clicked the pencil icon or accompanying text, turning editing mode off.
When editing mode is off, most of the developer features that are displayed in App Studio are hidden; this includes the control for switching between App Studio and Dev Studio.