Enforce dropdown value based on the value on other cells.

Hi, Could you please help with the following?

I have seven questions with answers organized as drop-downs and free-texts.

Q1 is a dropdown with options "Approved" and "Not Approved" (default option is "Not Approved"),
while Q5 is a dropdown with options "Onboarded" and "Not Onboarded" (default option is "Not Onboared").

I want to enforce the following:

1. Answer to Q1 can be changed to "Approved" only if the values in Q2, Q3, and Q4 are not blank (i.e. an error mark appears saying "you need to respond to questions before approving".

2. Answer to Q1 can be changed to "Onboarded" only if Q1 is equal to "Approved" AND the values in Q6 and Q7 are equal to "Yes". ((i.e. an error mark appears saying "You cannot onboard while the customer is not Approved or when the answers in Q6, Q7 are not equal to "Yes")

3. Additionally, how can I make conditional formatting so that cells C6, C8, C10 are filled in with red color when empty and turn into green when they are not blank?

Thank you for your help. excel is attached.