Multiple entry of "Date" with Data Validation in to a single cell.

[Gajendran Yadhav]

I'm working on a sheet where I'm keeping an entry of data on date-wise.
One column - Column K is for recording the particular date.
I have enabled data validation for this. I'm able to input only one date.

Is there any possibility that I can add multiple dates into the same cell, each separated by a comma.?
Eg: 01-02-2023, 05-03-2023, 07-06-2023, 27-07-2023, 22-08-2023, 13-09-2023 and so on.

Similarly in Column O & Column P, I've data validation function for List and Dependent List.
Column O accepts only either of the two value which I entered in the List...whereas, Column P arbitrarily accepts any value that I type into irrespective of the value in Column O.
How to rectify this.??

Note:
Column O Column P
By By Against
Against CD Civil
Civil Criminal
Criminal FIR
FIR TPC
WC

when I manually type into the cell, Column O accepts only either By or Against.
Even when column O is blank, Column P accepts manual entry. Moreover, it accepts any value say "asdjasjh" or "qwte214546gsjk" or "2135shdgfui"etc. However, when I enter the value in Column O, it clears the contents in column P.