It might take a few months to a year or so. depends on the complexity of the case.

I doubt that more employees filing a complaint will make the case go any faster. If it involves more parties, it will be generally slower.

If i remember correctly, generally 2k below. but between 2k-5k they still can take in complaints under DG's power.

Well, you can always sue the company for payment ma. Whether worth suing or not is another different matter ad. The definition of employee under Employment Act 1955 generally only covers those earning 2k and below.