Additional course with ca and bcom

Yes you can pursue other course beside CA by filling in form no. 112

but i have already filled that form for bcom during my article registeration. 

Should i apply again for CS also??

i heard that one can do only 1 addition course with CA which is Bcom in my case

Yes. ICAI allows only one additional course to be purused during the period of articleship training at a time. So, in your case ICAI wont allow you to pursue CS. You can pursue it only after completing your B.Com.