The Official marshmallow rom for YU Yureka, Yuphoria, Yutopia, and Yunique is now available.This YU OS is in beta mode and will be available for all the YU custom via OTA soon.Till then if you want to install official YUOs based on Android marshmallow on your yureka and Yuphoria then you can head towards official Yu Developer website.
Follow the steps given there to install official marshmallow rom on yureka (beta) and another device of Yu.These might help me less stable but don’t worry the stable version will be released soon.So just visit above link for Yu developer website and follow the flashing instruction.
Android M for yutopia and yunique is not yet available it will be soon available there keep visiting for an update.You can install official cm13 in your device if you have root access follow below links for the official cm13 rom.