(1) Can mere adult chatting without the knowledge of the spouse be regarded as a mental torture as per law and can attract 498A/DV and punishable in the absence of any other proof of torture/violence of any kind?
This evidence in her possession will not constitute for commission of offences under dowry prohibition act or cruelties or domestic violence act. She is having nil knowledge about law and she is acting on the tip off based on the hearsay information alone but painting it a legal color.
(2) I have already changed the password of my mail account, deleted the chat from my mail and trash also. I asked my friend to do the same also to be safe. Myself and my friend never met each other in this period. Can those chats be retrieved by my wife by summoning yahoo/service provider persons in court after long 1.5 years???? Does the service provider store all chats and mails?
Service provider do not entertain individual's request to provide such details and moreover they may not preserve the details after a year or so. Further, even if she gets the details they are not admissible as evidence in law. Also, the chats will not constitute for adultery or any offence. Chats between two individuals or more cannot be defined as an offence under any law.
(3) I want to know whether the only photograph of the chat message is sufficient to take any legal action against me?
This evidence in her possession is not admissible in law or facts.Her case based on such flimsy and vague reasons will be rejected by court.
(4) Is there any case possible against my unmarried friend by my wife?
NO
(5) Can my wife summon my friend to court in the divorce case??
NO
(6) Can my wife make that girl as a co-respondent in DV/divorce case with me?? I dont want that girl to be unnecessarily in trouble as she is unmarried. Can my friend refuse to accept the summon in this case? What will happen if she does not appear?
She can make her co-respondent only if she provides valid proof for adultery, Mere chatting or holding somebody's photograph will not constitute adultery, the court may not entertain the case itself.
Moreover from where will your wife get her address?
(7) Will this photograph of chat be accepted as an evidence as per act because it has been collected by hacking my password illegally without my knowledge and consent??
You may repeat this question in any form but the answer is simple NO, i.e., this is not an admissible evidence as per law. and also this will not constitute grounds for adultery.
(8) Can I press cyber crime and right to privacy act violation against my wife for illegally accessing my Mail account if she produces it as evidence?
The burden of proof will lie on her hence first of all allow her to do the mistake and then think of contemplating any legal action against her accordingly.