With no money can i file a case

Visit your local Court and get information about the free legal aid cell. Go to them and explain your situation. Maybe they will be able to help / advise alternatives.

but your mother will have to proceed against your father please note, not you.

Visit the local court to get legal aid & your mother can file a divorce & maintenance petition on the ground of cruelty. But don't try this if you are doing it for fun just to harass your father. It may back fire on you all.

1.  Yes, your mother even at this age can file divorce case and get free legal aid as per law.  2.  She will also get maintenance from the income of her husband.  3.  Your elder brother, being mentally challenged, also will get maintenance.  He also can file his maintenance case free of cost.  4.  You will not get any maintenance as you crossed the age of 18.

Are U all staying in the same house of UR father, or is UR father is staying separately ?  Is he behaving in that manner since the beginning or developed it off late? If all of U can prove his cruel attitude , U can certainly get legal remedy.

I agree with the opinion and advise of learned advocate Mr. Chandrasekar.  It is your mother who has got to initiate the proceedings against your father for divorce and maintenance.  She can get free help from government legal services authority.

Thanks all of you for your valuable replies .

How much can I rely on Government legal authorities . Are they worth , I mean are there chances of money laundering ?. I think my father and his other relatives might lucre the Government legal authorities.

The subsequent question will not find an answer because nobody can give an opinion that there wont be corruption at any stage.  The reliability on government free legal help will depend on your decision.