You file a writ petition seeking proper compensation  against the acquisition of your property by the PWD;

Let the PWD appear before high court and express their concern and reasons in this regard.

the PWD is not the authority to declare that this sale is invalid for the reasons they state.

In fact the PWD should obtain permission from District collector if at all the collector has declared that this purchase is invalid.

The reason stated by PWD is unjustified and against natural justice besides an illegal act.

You can approach the high court with a writ petition seeking compensation as per the latest land acquisition act.

File writ petition in HC against PWD refusing to pay you compensation for forcible acquisition of your land 

2) take the plea that sale deed mentions that M does not belong to SC and compensation is payable to you as you are bona fide  purchaser of land 

If your seller is SC, you should have taken permission from Collector. Sale by vendor is invalid, but you can seek refund from your vendor with interest and cost of suit, file suit for recovery and criminal complaint for cheating against vendor.

Immediately file writ in High court for compensation illegal acquisition and high handedness of PWD.

Saleem has no say in the matter, so his blame cannot be consider.

Further you being bonafide purchaser of land, entitle to full claim and compensation in addition to Land acquisition compensation.

Dear client,  

I'm sorry to hear about the situation you are facing. Here are some possible courses of action you could consider:

Verify the authenticity of the caste certificate: You can request the authorities to provide a copy of the caste certificate produced by Saleem, and verify its authenticity. You could also check the authenticity of the certificate with the issuing authority. If it is found to be fake or invalid, it could help your case.

Seek legal assistance: It is advisable to seek legal assistance from a lawyer who is experienced in property and land disputes. They can help you with the legal process of claiming compensation for the land taken by PWD, and also guide you on how to deal with the issue of Mahender's caste status and Saleem's complaint.

File a complaint against PWD: If PWD has demolished your house without giving compensation, you could file a complaint against them for wrongful demolition and seek compensation for the damages caused.

Contact the state government: You could also approach the state government and bring to their attention the issue of the land purchase without permission, and request them to intervene and help resolve the matter.

Negotiate with Saleem: If Saleem is the person who has complained about Mahender's caste status, you could try to negotiate with him and try to arrive at a mutually acceptable solution.

It is important to gather all relevant documents and evidence related to your purchase of the land, the demolition of your house, and the complaint against Mahender's caste status. This will help you build a strong case and increase your chances of success in claiming compensation for the land taken by PWD

Need to see the documents relating to the property and complaint submitted by Saleem then only concise answer can be given.

You can file writ petition in the same