I am also working on Level 2 and just started Sprint 2 so my answers here are closer to a guess than based on real Anapan experience.
If I am understanding your question correctly, you are looking to get some more details on the logic behind the functions you have called out.
I believe that the first line item "Current Period?" is being used to flag whether a specific time period is the current period - it is then the input into the other line items in the module.
YEARVALUE is used in "1st Forecast Year?" to efficiently determine if a time period (in your example a week) is in the same year as the current period. This is rather interesting as YEARVALUE seems to typically be used to summarize a number value based on what the summary method of the line item...in this case though it is applied to a boolean.
Many years ago I programmed in a multi-dimensional database called Express; to have fastest code possible your tried to have Express implicitly loop through the data versus explictly doing so. I think that is what is being done here with YEARVALUE. You could come up with the same result using IF-THEN-ELSE logic but I bet YEARVALUE "implicitly" loops much faster then an "explicit" function such as IF-THEN-ELSE.
At any rate, will let experts weigh in as I am a junior newbie 😉