The Panels attribute "Hidden" can be toggled Yes/No?

And how to toggle a panel's "tofront" attribute on and off?

Only attributes considered as object properties can be assigned. If you navigate to our documentation site, on each object tag you will find a section called Object Properties. This will give you information on what can be manipulated for each object. 

https://files.rarewire.com/wordpress/2012/06/panel...

In the cases above, hidden is not assignable, however when you use a load tag, if will automatically reveal an image or web tag that have been set to hidden. 

As for tofront, once an object has been set tofront, it can not be set back unless it is deleted and created again through a class, so use this attribute sparingly.