The hadiths don’t tell us exactly what the role of those 50 women (who are among the 313) is. So anything we say will be pure speculation. The Imam will give them appropriate tasks.
It’s not impossible to reach that level. The more sincere and pious you are the greater the chance becomes to be one of them. The 313 are very sincere, very humble, submit 100% to God, accept His system 100%, and very firm in their faith, they don’t oppress anyone, they follow God’s laws unwaveringly, and they truly implement the teachings of the Qur’an and Ahlulbayt (a).
A true and faithful Muslim from other schools of thought can definitely join the Imam when he reappears and believe in him. However, those 313 are believers with complete faith—they recognize Imam Mahdi as their living 12th Imam and they believe in his leadership and the leadership of all the Imams. One who rejects the divine leadership of the Imams cannot be part of the 313
Here’s a clip:
https://youtu.be/109JyJ–RPA