RC912152144CN please tell me what Null means. ANd where is my stuff has it reached India?

NULL is a technique problem of the tracking system of China Post. When Chinese cannot be correctly translated to English, it shows NULL. Here it refers to that your parcel was delivered to beijing capital airport for customs check.

Also good news for you here that your parcel has arrived in India. Here is the update;
2014-05-23 12:58, INDIA, DIMC NEW DELHI 110002, Return item from customs (Inb), Air
2014-05-21 18:29, INDIA, KOLKATA FOREIGN LCAO, Send item to customs (Inb), Air
2014-05-21 16:33, INDIA, KOLKATA FOREIGN LCAO, Receive item at office of exchange (Inb), Air