fail!
this discovery of a 1,000 diameter planetoid in the Kupyer belt with a stable orbit is in no way related to the article about Planet X with an erratic orbit that approximates an intersecting orbit with the earth.
there are literally thousands of large objects like your last link in the kupyer belt. so this is just one of many. nothing special.
planet X is supposed to have an erratic orbit similar to a comet, come close to earth, with cataclysmic results. the article in your planet X link continues with saying as many as 2/3 of the earth's population will be killed or worse.
so, if you could be so kind, could you post a credible link about this planet X from a source that is somewhat mainstream?