Ags battery tonic will cost 55-60 rupees per liter if you buy whole carton of 12. Seller who sold you for 130 ripped you. Exide battery water carton could be purchased for 750-800 and it has 12 bottles of 1.25 liters.
New batteries are designed to be put to work just after half an hour. Initial charging is not required after pouring electrolyte since these self charge to useful level.
If electrolyte ratio was correct you should get s.g at 1250 or more when battery is fully charged.
10-20A charger will do the job charging UGS 220
I usually do not turn off my inverter while adding distilled water. In fact i have poured water when batteries were getting charged. Never anything bad happened. I pour water very slowly and with the help of funnel. But it is better to switch it off.
When battery deteriorates naturally it lose some of its specific gravity. If electrolyte was lost from any cell for some reason you may pour some electrolyte until s.g becomes equal to other cells.