Our WebNotification is interval based not event based. However, based WebFormType.aspx and WebServiceType.aspx reference sample, we could provide a workaround for your scenario.

In the sample, the notification will only be displayed if this line is executed:

collection.Notifications = new WebNotificationEvent[] { evnt };

An event object is added to the collection, in your case you will need to add a conditional block so the event will only be added if there is a difference in Grid row count.

Did you mean when user click on the modified header, the user will not be redirected to the day view? If so in the new DIV click event handler you will need to abort the click. Here is the snippet:

function ClickEventHandlerHeader(headerElem)
{    
    event.returnValue = false;
    event.cancelBubble = true;   
}

Unfortunately, our WebFileUploader will need to save the uploaded file to the WebServer hard disk (or a path set in the UploadPath property) for further processing. Our documentation also has more explanation for this issue on article "Walkthrough: Configuring Upload Location" and "Webfarm and multiple worker requests support with built-in FileStateServer"

If you would like, you could delete the uploaded file after the business logic has been successfully executed, but the uploaded file will need to be uploaded to the hard disk first.

The issue could be replicated in my environment. This issue is caused because the clicked area is the newly added DIV, in order to resolve the issue, we will need to invoke the click event of the original area when we click the new DIV. You will need to add a new onclick event in the newly created DIV. Here is the snippet:

Listener.Add(headerElem[i], "onclick", ClickEventHandlerHeader, headerElem[i]);

During this click event handler, you will need to invoke the click for the original element, original snippet from this post:

var inProgress = false;
function ClickEventHandlerHeader()
{
    if (!inProgress)
    {
        inProgress = true;
        if (this.dispatchEvent)
        {
            var e = document.createEvent("MouseEvents");

            e.initEvent("click", true, true);
            this.dispatchEvent(e);
        }
        else
        {
            this.click();
        }
    }
    inProgress = false;
}

In a multiple row update scenario, you will need to set some time before invoking another Update function call. Here is the snippet, using BindtoAccessDataSource.aspx provided sample, I add a client side function to update the first 3 row of data:

function EditRows()
{
    var grid = ISGetObject("WebGrid1");

    //Update first 3 row
    var maxLoop = 3;
    var idx = 0;

    var intervalObj = setInterval(function()
    {
        if (idx < maxLoop)
        {
            var selectedRow = grid.RootTable.GetRow(idx);
            var cells = selectedRow.GetCells();

            cells.GetNamedItem("ContactName").SetText(selectedRow.GetCell("ContactName").Text + " " + idx, true);
            cells.GetNamedItem("Region").SetText("Region #" + idx, true);

            selectedRow.Update(false);

            idx++;
        }
        else
        {
            clearInterval(intervalObj);
            intervalObj = null;
        }

    }, 500);
}

Another suggestion would be to use WebGrid BatchUpdate feature, by setting AllowBatchUpdate = "true" under LayoutSettings and invoking AcceptAllChanges after updating all the rows. Here is the snippet:  

function EditRowsV2()
{
    var grid = ISGetObject("WebGrid1");

    //Update first 3 row
    for (var i = 0; i < 3; i++)
    {
        var selectedRow = grid.RootTable.GetRow(i);
        var cells = selectedRow.GetCells();

        cells.GetNamedItem("ContactName").SetText(selectedRow.GetCell("ContactName").Text + " " + i, true);
        cells.GetNamedItem("Region").SetText("Region #" + i, true);

        selectedRow.Update();
    }

    grid.AcceptAllChanges();
}