How to use a button's click event in another form

First of all, remove all the public stuff (event handlers and controls) that you've done as that is not the solution to your problem.

Why do you need to know which button was pressed? I can't imagine a scenario where that would be needed.

If you need a Button to Click in Form due to something happening in Form2 then Form2 should raise an event that Form subscribes to, and in the handler for that event it should either call the handler for the Button's Click or call the Button's PerformClick() method.

// Form2.cs
public event EventHandler ReclickRequest;

private void WhateverItIsThatCausesThis()
{
    OnReclickRequest(EventArgs.Empty);
}

protected virtual void OnReclickRequest(EventArgs e)
{
    EventHandler eh = ReclickRequest;
    if(eh != null)
        eh(this, e);
}

// Form1.cs
// In method that instanciates Form2
    Form2 form2 = new Form2();
    form2.ReclickRequest = form2_ReclickRequest;
//

    private void form2_ReclickRequest(object sender, EventArgs e)
    {
        // Call the button's Click event handler or it's PerformClick method
    }

See here[