Answer from cs61c-eu (Tian Ming Ouyang 16017341) for Question 1
Since anything can be expressed in 0, and 1 the code of anything program is just nothing but that.  If someone would find out how the 0 and 1 were used, ie know what they represent, then they can change that binary to whatever they desire.  I assume you can put encrpytion in your code, but as we all know nothing is uncrackable since data can be anything.