For your first question regarding Revised loss returns being filed for first time, my view would be as follows:-
Your query touches upon two aspects of income tax Act?
1.Validity of Filing a Revised Loss Return where Original Return was filed on or before Due date u/s 139(1)
For deciding this we go straight to the Madras HC decision in CIT. v. Periyar District Co-Operative Milk Producers Union Ltd. (2004), where it was held that "There is no bar in filing Revised Return u/s 139(5) showing a loss for First time". This means, eventhough your original return was an income return, you may subsequently file a revised return u/s 139(3) showing a loss.
2. Whether the term "DEDUCTION" you have used implies Deductions under Chapter VIA?
If its a Chapter VIA deduction, then the deduction (Rs. 2.1 Lakhs in your case) shall have to restricted to the amount of Gross Total Income (Rs.1.2 Lakhs in your case). The excess of deduction available (Chapter VIA) over income cannot be carried over as a Loss and shall lapse instead.
However, if the term deduction is not a Chapter VIA deduction, then you may claim the loss by filing a revised loss return.
Hope this helps.