Yes, Micromax Bharat 5 pro does have the google assistant.
Yes, Micromax Bharat 5 does have the OTG support.
We have not come across any user's complaint about it so far. Since the model is new, you can expect that such issues reported by users only after a certain usage or time.
No. Micromax Bharat 5 has a mono speaker.
Yes, Micromax Bharat 5 pro has dedicated LED flash for the front camera.