My opinion on your Queries are as under:
1) If i want to get married with her, than it is possible and legal?
Opinion: First of all try to collect the divorcee issued by the court then marriage can be possible legally.
2) if a husband and wife are living separately then is there any provision in law that after how many years marriage would be termed as legally dissolved.
Opinion: without court decree the marriage can not be dissolve.
3) if i want to do Court marriage, is it possible? what is required for that.
Opinion: if she is legally divorce then no need to worry, it is possible.
below is a list of documents required for court marriage these documents have to be submitted along with duly filled application form with the prescribed fees.
1.Four Passport Size Photographs of both boy and girl.
2.Proof of Residence it can be a Voter Card / Passport / Ration Car / Driving License / Bank Passbook / Lease Deed / Rent Deed) of the concerned boy and girl.
3.A birth certificate or any document like Municipal Corporation Certificate, Xth or XIIth Examination Certificate, Passport, PAN Card of the concerned boy and girl.
3.If any party is divorcee – Certified copy of Decree of Divorce granted by the Court.
4.Death certificate or divorce decree whichever is applicable, in case one of the parties had any marriages in the past.
5.If any party is a Foreign Citizen or holding a foreign Passport or is having foreign residential address – Certificate of Present Marital Status of the party / No Impediment Certificate / NOC from concerned Embassy and Valid VISA.
4) How the Girl parents can made this divorced legal now, is there any provision in law, like they can get some paper work signed by her earlier Husband. shortest way of making her divorce legal, so that i can marry her in next 2-3 months.
Opinion: Court Decree is mandatory for legal divorce, they file a MCD before Family court and get the divorce decree.