Hello student the eligibility to do CA articleship is you need to clear both group of ca intermediate (IPCC). After clearing you're eligible to apply for CA articleship. You need to fill the form on ICAI website you can also apply separately in firms/under ca for articleship. Big 4 is one of the most challenging companies to get in because you need to go through multiple test for it.

Feel free to comment if you have any doubt

Good luck