false marriage promise

in your case, you have consented but under the false belief, intentionally orchastrated by your bf, of getting married with your bf. 

once case registered, you will get a prosecutor.  also you can reach out to free legal aid services in your area.  go to the district court of your area, and ask for the legal aid department. you shall be provided with a lawyer there. 

and as you already know, you will have to prove certain things in the court room, the accused also receives a chance to clear the allegations brought against him. He, in his turn, can state any reason which may appear plausible, and if proved that 'he had intention before, but subsequently the intention changed, due to factors, not owing to mala fide', may cause you to lose the case. 

if his intention changed then he should have stop before ,how could he continue 10yrs relationship and unkwn about own gf nature, fact is he never had intention of marriage , he used for lust, his mom against bcoz of caste and now making any excuses to ascape from it by blaming me . he hide relationship from all people that proves he is cheater. and frm 2months he blocked me. i never wanted physical relation before marriage i cleared still he forced and blackmailed me by various things. and unnatural things.
what should i write in FIR. it should be short lines or details ?

After 10 years of relationship for which throughout these years neither you objected nor made complaint against him for forced s*x or unnatrual s*x, whether on promise of marriage or not, marriage that you must be looking to take place since last 10 years, but now you want him to be criminally prosecuted. I doubt if that will be possible. The Police will record your statement and ask you all the relavent questions, especially why there was delay of 10 years for filling the complaint against him. The unnatural s*x is an offence where even the consent of other partner is not relavent, but that too has to be proved with sufficient evidence for criminal prosecution, mere your statement will not serve the purpose. The charges of Rape and indulging unnatural s*x are State criminal complaint cases where FIR has to be registered for which you don't need and any lawyer, you can go and register the complaint directly with police if you so desire.