I have been working for Instellars for more than an year now and saw enough to write a review.
The management will speak to you differently once you join the company. If you are made a promise for onsite then you have to be incredibly lucky to get through.
Once you join, you will be put as a subcontractor to other companies and you will get step motherly treatment. There aren't many clients for this company, 1 or 2.
So you might get fired within weeks of joining.
Even if you work your very hard for the client you will not get any benefits since the company is very small and you getting salary on time itself is a great thing.
Take a look at all the earlier reviews most of them are written by the same person on 22 Aug 2018, it is the social media manager of the company and not by the consultants. Join only if you have no other choice.