Well, I'm not an expert in VBA but you should do some search in this site 'cause this site's the best to find answers.

Answer for question 1.
You can create buttons to open all comments to see if any comments have image and another button to close all comments

Create a button, insert new module in VBA windows and assign this macro to the button
Sub ShowSheetComments()
'shows all comments on the active sheet
Dim c As Comment

For Each c In ActiveSheet.Comments
  c.Visible = True
  c.Shape.Fill.ForeColor.SchemeColor = 5
  
Next

End Sub
Assign this macro to second button to close all comments
Sub CloseSheetComments()
'shows all comments on the active sheet
Dim c As Comment

For Each c In ActiveSheet.Comments
  c.Visible = False
Next

End Sub

Answer to question 3.

check this site
http://www.mrexcel.com/forum/showthread.php?t=257081
Cheers mate