Q1 - FizzBuzz

Q2 - Word/Stack Machine
https://repl.it/@mb389/stack-machine
https://github.com/motyim/ProblemSolve/blob/master/src/main/java/me/motyim/codility/StackProblem.java

POP: Pop the elements from the stack.
DUP: Duplicates top element, makes a copy of it and places it at the top of the stack.
+ : Pops top two elements, adds them and places the sum to top of the stack.
- : Same like + except it subtracts top element with second top element.

Q3 -

Solution for Q3 -
https://www.careercup.com/question?id=5689704156495872