1. Write a Python program that takes three integers as input and finds the maximum among them. Prompt the user to enter the three numbers and print the maximum value.
2. Write a Python program that determines if a given number is even or odd. Prompt the user to enter a number and print the appropriate message.
3. Create a program that prompts the user to enter their age. Based on the age entered, check if they are eligible to vote. If they are 18 or older, print "You are eligible to vote." Otherwise, print "You are not eligible to vote yet.
4. Create a program that asks the user to enter their exam score out of 100. Based on their score, display the corresponding grade using the following criteria:
   • Scores above or equal to 90: 'A'
   • Scores between 80 and 89: 'B'
   • Scores between 70 and 79: 'C'
   • Scores between 60 and 69: 'D'
   • Scores below 60: 'F'

Note: Remember to use if-else and elif statements to solve these problems. Test your programs with various inputs to ensure their correctness.