Both are possible to accomplish.
For showing only the appbar icons relevent to the page you can use the Panorama.SelectionChanged Event:
var currentPanormaItem = ((Panorama)sender).SelectedItem
if(currentPanormaItem.Equals(firstPageItem))
{
// Set AppBar icons for first page
}
else if(currentPanormaItem.Equals(secondPageItem))
{
// Set AppBar icons for secondpage
}
If you know which panorama item is selected you can set the appbar icon accordingly.
Changing the selected item of a Panorama can be accomplished like this:
panoramaControl.DefaultItem = panoramaControl.Items[indexToSet];
Though changing the selected index of a Panorama is possible, I would advise using a Pivot control. With a Pivot control it is easier to keep track of the selected item and you get a nice animation when you programatically switch the selected page.