Theft by finding

Please explain how ownership and unlawful possession of objects get defined while in public place. Suppose I find a purse in a train station and before I can submit it to the station master, police tracks it and charges me for theft. How does an owner claim his/her right on an object that is in his/her immediate possession? Is anything in a person's hand/pocket his/her(while in public place) property? If not, then how to define ownership? Also what about objects that are not in his/her immediate possession? Suppose luggage tucked away below seat; is it completely the owner's responsibility to make sure nothing gets stolen? What about about cars parked on roards and stalls on road or on footpath? I also want to know the actual owner's rights. Whether an owner is allowed to use physical force on a person in immediate or past possession of his/her property, and if yes, then under what condition and to what degree? Do the onlookers have any duty or right to meddle? If yes, then please explain. What if a person possesses legal firearm? Is the person allowed to use the firearm in public to prevent a theft or catch a suspected thief? Is the person allowed to shoot? I also want to know if the laws are same in every state ofIndia and apply similarly for all Indians.If the owner is a police officer or judge, can things go differently? Have these laws been changed significantly in recent times(after independance)? Pls forgive any grammatical or lexical mistake. I am not a law student. Please explain in layman's terms.