About submission of documents for visa application by my freinds?

Yes, yo cna entrust your friend to submit the application for you on your behalf, but you have to be interviewed in person if the embassy of China requires.
By the way, I hear that now China Embassy in Malaysia only accept visa application from diplomatic and service (official) passports holders, and ordinary passport holders should apply for the China visa thrugh the China Visa Application Service Center on the 2nd Floor, Plaza OSK, 25 Jalan Ampang,50450 Kuala Lumpur, Malaysia.