Can my wife claim spousal maintenance without fomal divorce ?

My marriage is almost 20 yeats old and solemnised according to Christian rites as both of us are christians. we had unreconcilable differences and lots of them that our marriage is on the verge of dissolution. I have two children, a 18 year old daughter and a 12 years old son. My wife is a graduate but not working. She is getting a monthly income of around 20k through house rent after adjustment of housing loan. I am a State government employee having a take home salary( aftr deductions) is 34K. Im living separately since last 2 years without any sort of contact with my wife nor with my children. Now Ive heard that my wife has filed a maintenance petition in the Family court. Due to my transfer i could not receive the notice and same has been returned by postal authorities. Present address of my residence is not known to my wife/ In this connection I would like to know 1) whether the court can grant maintenance to my wife without a divorce or separation? 2) what would be the amount of maintance I would be asked to pay? 3) Can I take paying the maintenance as a precedent for me to file a divorce petition? 4) Can I demand the custody of my son during the Maintenance proceedings?