Well as a matter of fact L920 has the same problem too it drains automatically like u said , I think it might be a factory defect for all L1520 ,maybe ask some who has a L1520
Soft reset might do the trick or do the following make ur brightness low and turn of those vibrations of touch keys,make ur touch sensitivity to normal that's is man or ask other L1520 users
If it is a class 4 then it might take more than 15 min , so if ur gonna use ur sd card as ur primary storage then u might want to upgrade to class 10 , that's my choice. I myself using 32gb SanDisk class 10
Re: why cortana doesnt work in india
Cortana alpha is already available in India with cyan but we still don't have the indian language package for that indian accent so it might take a while, but may be available with windows phone 10 soon