Hi!
Here I added some more event macro in the same sheet. "Case 1", "Case 3" and "Case 4" are added. "Case 2" is the same Macro discussed above.


Code:
Private Sub Worksheet_Change(ByVal Target As Range)
' Case 1
    If Target.Address = "$I$20" Or Target.Address = "$U$20" Or Target.Address = "$Z$20" Then
        If Target.Value = "" Then  '  case a cell was emptied
         Let Application.EnableEvents = False
         Let Target.Value = ChrW(&H270F)
         Let Application.EnableEvents = True
         Let Target.Font.Color = -3817475
             Target.Font.Size = 9
        Else  '  case a text was entered
         Let Target.Font.Color = -12316781
             Target.Font.Size = 12
        End If
    Else  ' Target is Not a cell to be acted on
    End If
    

' Case 2
    If Target.Address = "$J$19" Or Target.Address = "$J$19:$P$19" Then  '  we need  "$J$19:$P$19"  to make macro work on  Delete  probably because of merged cells
    Dim RngTgt As Range: Set RngTgt = Target
        If Target.Address = "$J$19:$P$19" Then Set RngTgt = Range("J19")
        If RngTgt.Value = "" Then
         Let Application.EnableEvents = False
         Let RngTgt.Value = "(Select Here)"
         Let Range("R19").Value = ""
         Let Application.EnableEvents = True
         Let RngTgt.Font.Color = 10855845
             Range("R19").Validation.Delete
             Range("R19").ClearComments
        ElseIf RngTgt.Value = "Nuclear Family" Or RngTgt.Value = "Joint Family" Then
         Let Application.EnableEvents = False
         Let Range("R19").Value = "(Remarks if any...)"
         Let Application.EnableEvents = True
         Let Range("R19").Font.Color = 10855845
         Let RngTgt.Font.Color = 6751362
             Range("R19").Validation.Delete
             Range("R19").Select
             Range("R19").ClearComments
        ElseIf RngTgt.Value = "Single-Parent Family" Then
         Let Application.EnableEvents = False
         Let Range("R19").Value = "(Select Reason for Single-Parent)"
         Let Application.EnableEvents = True
         Let Range("R19").Font.Color = 10855845
         Let RngTgt.Font.Color = 6751362
            With Range("R19").Validation
              .Delete
              .Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:= _
              xlBetween, Formula1:="Expired {One is No More},Divorced {Separated Legally},Break-Up {Attachment Hampered},Abandonment {Fully Separated},Enter Reason Manually"
              .IgnoreBlank = True
              .InCellDropdown = True
              .InputTitle = ""
              .ErrorTitle = "Error!"
              .InputMessage = ""
              .ErrorMessage = "To enter the reason manually, please select the option 'Enter Reason Manually'"
              .ShowInput = True
              .ShowError = True
            End With
             Range("R19").Select
             Range("R19").AddComment
             Range("R19").Comment.Visible = False
             Range("R19").Comment.Text Text:="Reason for Single-Parent"
        ElseIf RngTgt.Value = "Uncategorised" Then
         Let Application.EnableEvents = False
         Let Range("R19").Value = "(Please Specify the Case)"
         Let Application.EnableEvents = True
         Let Range("R19").Font.Color = 10855845
         Let RngTgt.Font.Color = 6751362
             Range("R19").Validation.Delete
             Range("R19").Select
             Range("R19").ClearComments
        End If ' end of all values of J19 to  result in actions
    Else  ' Target is not cell J19  ( or  J19:P19 )
  End If
    If Target.Address = "$R$19" Then
        Let Target.Font.ColorIndex = xlAutomatic
        If Target.Value = "Enter Reason Manually" Then
        Target.Validation.Delete
        Target.Value = ""
     Else
    End If
   Else  ' Target is not R19
 End If

' Case 3
If Target.Address = "$J$21" Or Target.Address = "$J$21:$P$21" Then
    Dim RT As Range: Set RT = Target
        If Target.Address = "$J$21:$P$21" Then Set RT = Range("J21")
        If RT.Value = "" Then
         Let Application.EnableEvents = False
         Let RT.Value = "(Select Here)"
         Let Range("R21").Value = ""
         Let Application.EnableEvents = True
         Let RT.Font.Color = 10855845
        ElseIf Not IsEmpty(RT.Value) Then
         Let Application.EnableEvents = False
         Let Range("R21").Value = "(Remarks if any...)"
         Let Application.EnableEvents = True
         Let Range("R21").Font.Color = 10855845
         Let RT.Font.Color = 6751362
             Range("R21").Select
        
        End If
    Else
  End If
     If Target.Address = "$R$21" Then
        Let Target.Font.ColorIndex = xlAutomatic
     End If


' Case 4
If Target.Address = "$J$22" Or Target.Address = "$J$22:$P$22" Then
    Dim T As Range: Set T = Target
        If Target.Address = "$J$22:$P$22" Then Set T = Range("J22")
        If T.Value = "" Then
         Let Application.EnableEvents = False
         Let T.Value = "(Select Here)"
         Let Range("R22").Value = ""
         Let Application.EnableEvents = True
         Let T.Font.Color = 10855845
        ElseIf Not IsEmpty(T.Value) Then
         Let Application.EnableEvents = False
         Let Range("R22").Value = "(Remarks if any...)"
         Let Application.EnableEvents = True
         Let Range("R22").Font.Color = 10855845
         Let T.Font.Color = 6751362
             Range("R22").Select
        
        End If
    Else
  End If
     If Target.Address = "$R$22" Then
        Let Target.Font.ColorIndex = xlAutomatic
     End If

End Sub
I have 2 question here...

1. Case 2 have line
Dim RngTgt As Range: Set RngTgt = Target
,Case 3 have line
Dim RT As Range: Set RT = Target
, and Case 4 have line
Dim T As Range: Set T = Target
I have more than 20 cases which are to be added in the same event macro given above. So is it necessary for me to define the range everytime with a new name (as RngTgt, RT & T)??
Or there is some other easy method available to solve such cases??

2. Case 3 and Case 4 are almost same. The only difference is - Case 3 work on Row 21, while Case 4 work on Row 22. So, is it good to keep them as they are, or there is any way to merge and refine them??