Hindsight is 20/20, or is it 20/20 Hindsight? You be the judge

Music
#1

https://www.youtube.com/watch?v=hi4pzKvuEQM

#2

https://www.youtube.com/watch?v=6vopR3ys8Kw

#3

https://www.youtube.com/watch?v=aP_-P_BS6KY

#4

https://www.youtube.com/watch?v=CwpARGF4Zmk

#5

A song everyone must remember.

https://youtu.be/lH3hrtp1T84

#6

This one too. Another must.

https://youtu.be/IdpzlwKWWss