Basically, NoCanDo is implying that people steal his style. To be swagnostic can be interpreted as having gnosis, meaning knowledge in Greek, of swag.
He could also be referring to agnosticism, the view that the existence or non-existence of any deity is unknown and possibly unknowable. Swagnostic could be seen as a portmaneu of ‘swag’ and ‘agnostic’, referring to him being a swagged out agnostic.
Also, it could be a possible reference to Chess Records which was a record label based in Chicago. Famous for having many artists such as Chuck Berry that influenced later rock bands. The Rolling Stones have a song entitled 2120 South Michigan Avenue which is a reference to a location of Chess Records where the song was actually recorded.
Chance is, also, referring to an old famous song http://www.youtube.com/watch?v=bjNSmAl7hF0
Earlier in the song, Em says he prematurely ejaculated on her belly which is “below the ribs”
Weeknd reference?
Yes, it is a nod to the motif of Jay-z’s but “black star” is an obvious nod to the rap group of the same name (Mos Def and Talib Kweli). Gambino is a fan of Mos Def
‘black star" might, possibly, be a reference to the Talib Kweli and Mos Def rap group