Part B)

I am slightly puzzled why you are not simply adding a drop down list here, as in Cell J19

I am not sure why clicking on a cell should be required to make something like a drop down list for that cell. Why not just make a drop down list for that cell?

I think I was unable to explain my points clearly. The reason for not adding a drop down list in the cell "R19" is-

As per my knowledge, a normal drop down list made by Data Validation tool, allows the user to enter the only values which are defined in the data validation list. That is, if the drop down list have only 2 menu, say "A" and "B", the user can not enter any other value in the cell other than "A' and "B".

Here, in my case, I've several occasions when I have to type many things in the cell "R19". I have to use the drop down list in the cell "R19" in only one case, and the case is "If cell J19 contain the value Single Parent Family". In all other cases, I need to enter data in the cell manually.