What code in java do I use to exit program or end program in CMD?

You needed to break. I have added that in if ( attempts1 == 0 ). Now it should fix your problem.

while( attempts1-- > 0 && !answer1.equals( ans1 ) ) {
            System.out.print( "What is your guess? " );
            ans1 = sc.next();

            if ( ans1.equals( answer1 ) ) {
                System.out.println( "You guessed correctly!" );
                attempts1 = 3;
            }
            else {
                System.out.println( "Incorrect. Attempts remaining: " + attempts1 + " What is your guess again?" );
            }
            if ( attempts1 == 0 ) {
                System.out.println( "Game over.." );
                break;
            }
        }

you are trying to check the value of input with correct answer in loop, so adding it to loop to check each time is redundand:

you can make the application to close after the correct answer found by using break keyword or 3 wrong attempt:

while (attempts1-- > 0) {
    System.out.print("What is your guess? ");
    ans1 = sc.next();
    
    if (ans1.equals(answer1)) {
        System.out.println("You guessed correctly!");
        break;
    } else {
        System.out.println("Incorrect. Attempts remaining: " + attempts1 + " What is your guess again?");
    }
    
    if (attempts1 == 0) {
        System.out.println("Game over..");
        System.exit(0);
    }
}

Based on the code you posted, I guess there is another bigger loop that loops through questions. So you need to stop the bigger loop too, with a flag. Something, like this:

for (String answer1: answers) {
        boolean gameOver = false;
        while (attempts1-- > 0 && !answer1.equals(ans1))
        {
            System.out.print("What is your guess? ");
            ans1 = sc.next();

            if (ans1.equals(answer1)) {
                System.out.println("You guessed correctly!");
                attempts1 = 3;
            }
            else {
                System.out.println("Incorrect. Attempts remaining: " + attempts1 + " What is your guess again?");
            }
            if (attempts1 == 0) {
                System.out.println("Game over..");
                gameOver = true;
            }
        }
        if (gameOver) {
            break;
        }
    }

There are a lot of suggestions to use System.exit(...) - which is technically the correct way to exit an application if there's a good reason to do so. However, in your case, you have a loop that you should exit and that's not working - which says that the problem is in your loop condition.

Anything else, be a it a break or a System.exit(...) call is just bypassing the fact that there's actually a problem somewhere else.

With that said - if I run your code exactly as it is, it behaves as expected. So what other code is around that that we can't see?