I am a fifth-year student at a top-tier NLU, considering going abroad for an LLM next year.

In the event I am unable to find a job outside India, and I am forced to come back, would it be easy for me to find a job at a Tier-1 law firm?
What would the process be like?

It won't be easy. But it may give you a headstart, depending on your university, specialisation, grades and extra activities during your time abroad.