Hi Nisha,
Wonderful to hear about your path!
The 'Introduction to Pali' is a buffet of mixed materials. You may partake in them in any order and there are no tests other than some Quizlet flashcards and activities embedded in some units/lessons.
If you are new to Pāli it might be worth while to finish the syllabus (PDF or web version) of Introduction to Pāli Grammar and Pronunciation before moving on to Exploring the Path or Buddhasahassnamavali.
But of course also each lesson can also be studied at random. The whole school is informal studying of the language.