I can’t get the following statement, why would arithmetic mean be a better instrument than the geometric mean? Should not the geometric mean be more accurate!
_ “Compared with the geometric mean return, the arithmetic mean return is consistent with the assumptions of single period models, such as the CAPM.” _
Geometric mean would be better for multiple periods while arithmetic is better for single periods.
You forget your L1 material huh? This is straight from L1.
This is true, over studying for L2 made me forget L1 
Maybe you would share a few tips regarding how the less fortunate can never forget anything and remain full of their confidence?
Its simple. Understand the material rather than memorize the material. Some stuff still forgets as the breadth is huge, but I try to retain the core material rather than the obscure.