This league doesn't explicit to use 3 compounds compulsory, but you're given a number of limited set of compound each season (nominated by you). If you used up a compound then you cannot use that compound or facing a penalty.
You can check the upcoming season and the rule here.
|MTWTFSS at 14:00|
|75% race distance igp-car 2 cars per team 2.0x race speed|