Can I speak in Hindi in an interview or group discussion?
If you are applying for a position in a multinational company which specifically requires you to communicate with overseas clients, customers then fluency in English is a must. Speaking in Hindi or in any other Indian language during the recruitment process for such positions will be suicidal as your interviewer will immediately disqualify you as not being suitable for the job.
On the other hand, say if you are applying for a government sector job and the job requires you to interact with local people then speaking in Hindi or displaying fluency in the local language might as well work in your favor.
Also in some jobs like in core engineering fields, the recruiter is more bothered about your technical know-how and not on your communication skills. In those interviews or GDs, if at any point you feel that the language is creating a barrier in the communication process and is preventing you from explaining things correctly, you can always ask for permission from the interviewer or the moderator in group discussion to switch language and continue in Hindi.
Let me know what are your thoughts on this topic in the comments section below.