Remember, only the exercises marked with an asterisk are required for the certification. This is important because the exercises change regularly, but the project requirements are more stable.
Now, however, if you look at my profile it shows a project history that looks like swiss cheese. I’ve only done about half the exercises. All those I “missed” have actually been added in since I did my exercises.
That’s okay, though! They are there if I need to brush up on a topic, and not having them doesn’t affect my path towards certification at all.