Is my lawyer is correct or trying to cheat me

you must desist from making any forged document and filing suit on its basis. your opponent can demand  its lab checking and you will be trapped in criminal cases.

Your question that  "Will lawyers cheat their client?"- Lawyers are also human beings having same blood, senses, ideas, sentiments, greediness etc., so there cannot be any surprise if a lawyer cheats his client, though they are not supposed to betray the trust reposed on them by their clients.  Every crime has a legal remedy.  A complaint against the lawyer can be lodged with the local bar association besides the Bar council of India, and if the fraud can be proved by evidence, a criminal complaint also can be lodged, so please decide accordingly.