cell protection;auto insert row with formula and overtime computation

Hi everyone!

Greetings of good health!

My problem as follows:

1. How can I or is it possible to protect a cell(s) without entering a password? so the user can use the particular cell (colored dark blue)?

2.Is there a way that a user can auto insert/add row and copy the formula in a click of a button?

3. In computing the overtime hours what will be the formula if the conditions are: a. in weekdays (every Mondays to Fridays F10;G10) the start of overtime will be 6:00PM; b. in weekends (Saturdays and Sundays F12;G12) the lunch break (12:00pm to 1:00PM) is not computed in the overtime hours.

4. How to come up with the result in 0:00 if there is no time entry were encoded?(N11,N14 to name a few)

Attached is my sample file.

Thank you in advance.