Applications of stack:
1. Reversal of string: We can reverse a string by pushing each character of the string on the stack. After the whole string is pushed on the stack, we can start popping the characters from the stack and get the reversed string.
2. We can use stack to check the validity of an expression that uses nested parentheses.
3. We can use stack to converting infix expression to postfix expression using stack.
4. False, because We can evaluate prefix expression using stack same like postfix evaluation.