How Can Set Probity from another form

Just create a property in the new form which does that for you:

public class Form1: Form
   {
   ...
   public bool ShowImage
      {
      get { return pictureBox31.Visible; }
      set { pictureBox31.Visible = value; }
      }
   ...
   }

And set it's value before the call to ShowDialog:

Form1 fm = new Form1();
fm.ShowImage = false;
fm.ShowDialog();

If you use ShowDialog, then the call does not return until the form is closed, so the setting of it's properties must be done before you display the form.

You could use Show instead, but then you'd want to add a FormClosed event handler to detect when the user closes it, and either re-display your old form, or close the application.

BTW: Do yourself a favour, and stop using Visual Studio default names for everything - you may remember that "TextBox8" is the mobile number today, but when you have to modify it is three weeks time, will you then? Use descriptive names - "tbMobileNo" for example - and your code becomes easier to read, more self documenting, easier to maintain - and surprisingly quicker to code because Intellisense can get to to "tbMobile" in three keystrokes, where "TextBox8" takes thinking about and 8 keystrokes...