MacBook Pro - not booting - going around in loops?
Have you had a luck with it yet? 

Sound like it may be similar to mine. Logic board for Mac Book Pro's sold between late 2011, whole 2012 and start 2013 are under Apple's Extended Warranty Program. Your symptoms are the same as what I had before mine completely died. Going in tomorrow to have my logic board replaced for free. Thanks Apple. 

Please see the link below. 

https://www.apple.com/support/macbookpro-videoissues/

Hope this helps.