In level 1, before the test you are advised to download a clean and complete version of the model to do the test.
And as @Misbah advise the content contains all of the answers so it is worth taking notes and going over the learning centre content. The on demand videos give hints by making key points, so I woud make a note of these too.
It is readily available you can download it but if you want to practice you can build it as well.
If you are 299 certified then just download it and follow the instructions of uploading the files as and when required and if you are not then continue building it and make sure you watch all the videos and go step by step
Yes you can download a clean model for the certification exam for Level 1 and this is what Anaplan advises you to do.
I would recommend to attempt to build the level 1 model also as this will really support your understanding of how the platform works and its capabilities. This is one the best things about level 1 is that it really builds your knowledge of the Anaplan platform.