<plugin name="pano" url="pano.png" align="top" x="-60" y="10" onclick="forma_px(600,400,http://www.ipad.classic-ru.org/tzar/ph01.htm,);" onhover="showtext('panorama')" />
<plugin name="object" url="obj.png" align="top" x="4" y="4" onclick="forma_px(600,500,http://www.krpano.com/objects/oldslr/,);" onhover="showtext('object')" />
<plugin name="panpan1" url="panpan.png" align="top" x="80" y="10" onclick="forma_pct(0.7,0.6,index.htm,);" onhover="showtext('call itself')" />
<plugin name="panpan2" url="panpanpan.png" align="top" x="160" y="10" onclick="forma_pct(0.8,0.7,pk14.htm,);" onhover="showtext('pano-in-pano-in-pano...')" />
There are no special technic to open fullscreen mode in pano inside pano. Here you can see the fragment of code that we use to create that example.
I have tested example on different systems and browsers. On some systems it open fullscreen mode always, on some only when you include single pano in pano. I can't explain you this behavior.