Not Getting Paid By A Company? Work-from-home Intern

I interned for a company called as XXX or XXX (End to End Marketing Platform. It takes a large number of work-from-home interns from IITs and other top colleges and gives them tasks in various domains. In the middle of the internship when you’ve done some work, they’ll say your performance is poor and release you without any pay. I did the work what was assigned to me and the CEO YYY gave more work which I couldn't complete in time, but he released me off saying that I didn't do the extra one which wasn’t mentioned in the job description. Till today he hasn’t given me any money nor any certificate. I don’t know what to do! I haven't met any of them but I signed NDA and offer letters. Can you'll help me on this?
[Edited: please focus on the problem instead of naming companies or individuals]

Simplest way is to lodge a complaint with your local police station under Cheating, Indian Penal Code. Also there was clear violation of Info Technology Act. There may be few more cases out there. Search the net for such cases show the officer that too.
Also show the same to your area labour inspector. Also go to PF and ESI department. All such compliance's are also not met by these companies normally. So you can grab them there. For the coverage and other in such acts see website below as I cannot list all here.

Dear Candidate,

It takes a large number of work-from-home interns from IITs = Correct

In the middle of the internship when you’ve done some work, they’ll say your performance is poor = Incorrect

1. Will someone accept that if he/she has actually not performed !! You are live example, How you proof you have actually worked as per desired results.

2. Most of our internships are posted in groups of minimum 3 candidates, we compare your work with other candidates and only if you have done very pathetic with respect to your peers, we hold candidate's stipend.

gave more work which I couldn't complete in time = Most probably he has given you second chance to perform and you have accepted on own that you have failed even in that second chance.

drop your details to [Login to view], we will issue certificate to you immediately not matter even if you have not performed, but to motivate you

you are mistaking project detail document as offer letter, Offer letter is generally for part/full time employees.

Can you'll help me on this? = Yes, we will drop details to [Login to view]

Depending on the terms and conditions of NDA as well as offer letter as well as any other communication in writing made between you and the company and vice versa, you next course of action can be decided.

You need to take it up with the placement in charge of your college. As per your post, many students have some or the other problem with the company. All of you need to put up the problem to the placement in charge and get this company banned from your college to save future mishaps. Also, you need to send this resolution to all the IIT's, so that they could also consider similar action. An intern not being paid, very well reflects the value system of the organization. An intern is an on the job trainee and he needs to be mentored for the task to be completed. He is not an employee. If the intern's performance is poor, it means the problem is with the mentor and not the intern. Your college needs to also write to them about the poor quality of mentor ship and take it up strongly with them asking them to issue the certificates and also the stipend.

How are these schemes any different to other so called "work from home" scams.
I have posted many, many times, warning people NOT to engage in any "work from home" schemes, as they are almost certainly SCAMS.
A lot of them have been advertised on CiteHR over the years. I would be interested to hear from any member who has been successful with this sort of work.
However, I strongly suspect, many of you have been cheated.