You can find a lot of past papers that will prepare you for Round 1 under ‘Start Solving Problems’ on the homepage.
Have a look at the Round 2 past papers, and bare in mind that the main difference between round 2 and round 1 is that in round 2 you will be asked to provide explanations for your answers.
International Linguistics Olympiad (IOL)
You can find all IOL Past papers on the IOL Website: https://ioling.org/
Neema Kotonya has provided walkthroughs for 3 IOL questions:
Click to see the other two: