1. Does a constructive amendment occur where the jury instructions relieve
the Government of proving, as alleged in the indictment, that a defendant committed
a crime by using a "firearm," and where the Government argues that the defendant
could be found guilty of that crime even if he used a toy gun?

2. Does a material variance arise where a court declines to instruct the jury
that the Government has to prove, as alleged in the indictment, that a defendant
committed a crime by using a "firearm," where the Government argued prior to trial
that the use of a firearm was an element of the offense and stated that it would not
argue that the object used was anything other than a firearm, and where the
defendant's sole theory of defense depended on disproving that he used a firearm?

Whether a constructive amendment occurred when the jury instructions and government's closing argument allowed conviction for armed bank robbery without proof of a firearm as alleged in the indictment