
I know the “expected value of error term =0” is an assumption for both one independent variable and multiple regression. Is this also an assumtion for the Time Series?

Just ran into a EOC question 28 on page 405 of the first CFA book.
They mention the multiple regression model are subject to both parameter estimate uncertainty and regression model uncertainty. How do we test these two uncertainties seperately?
 Another question ECO question 17 from page 600 of the Volume 4 book.
They mention that "firm 3 was a cash offer in normal market conditions whereas firm 2 was a stock offer in a boom market and the value does not reflect risk and growth in the immdediate future." Why the stock offer does not reflect risk or growth? Shouldnt the stock price always reflect the market risk and company risk?
Thank you!