Hi there! For 7, this reaction is a conjugated hydrohalogenation which involves a production of 1,4-disubstituted and 1,2-mosubstituted product. The mechanism of 1,4 product requires a less stable intermediate which means it requires a very high energy intermediate. Check out Johnny's video on Conjugated Hydrohalogenation here: https://www.clutchprep.com/organic-chemistry/conjugated-hydrohalogenation/?c_id=14874
For 8, oxygen there has partial positive charge because it exceeds its bonding preference of 2.
Hope that helps!