I need help with this using ORACLE SQL Developer, and please can you explain how exist, ANY, =ANY works in this code

In ORACLE SQL: You need to find out the details of all employees who were hired for the job Id Sa_rep in the month of June 2013. Which of the following queries will give the required results?

1. SELECT first_name FROM employees WHERE employee_id exists (SELECT employee_id FROM employees WHERE TO_CHAR(HIRED, MM/YYYY) = 02/1981 AND job_id = SA_REP);
2. SELECT first_name FROM employees WHERE employee_id ANY (SELECT employee_id FROM employees WHERE TO_CHAR(HIRED, MM/YYYY) = 02/1981 AND job_id = SA_REP);
3. SELECT first_name FROM employees WHERE employee_id = ANY (SELECT employee_id FROM employees WHERE TO_CHAR(HIRED, MM/YYYY) = 02/1981 AND job_id = SA_REP);
4. SELECT first_name FROM employees WHERE employee_id = (SELECT employee_id FROM employees WHERE TO_CHAR(HIRED, MM/YYYY) = 02/1981 AND job_id = SA_REP);