1) what are terms and conditions of your leave and licence agreement ?
2) you would need landlord consent to make a kundi outside main door . the claim made for Rs 20,000 by licensor is outrageous . a lock does not cost more than Rs 500
3) in leave and licence agreement one set of keys is always with licensor so that he can after prior intimation to you inspect the house given on rent
4) you can keep a godrej locker inside the flat and keep it under your lock and key for storing your valuables .
5) in the alternative terminate the leave and licence agreement and seek refund of your security deposit if there is no lock in period