Yup, this example doesn't intend to solve all problems. Not sure if retrieving previous day price is possible. I just track day to day if I want to make comparisons.

You can reference this example sheet for #2: https://docs.google.com/spreadsheets/d/1yh6maB3wHUXyrkc5YU0x6IMAYdmDC7wmW_e6Cafy-aA/edit#gid=0

Feel free to FILE>Make a copy