The OS X updaters and combo updates kept on Apple download servers are not full installations, and require the previous, or same major release of OS X installed beforehand.
Even if you had downloaded the first Yosemite release from the OS X App Store prior to any subsequent updates, that same download attempt now, if available, would be 10.10.5 — which is in keeping with Apple maintaining only the last revision of OS X in the App Store. If you had never downloaded OS X Yosemite from the App Store prior to the El Capitan release, then you have no access to it — period.
It is a violation of the terms of use for this site to request others violate these terms by posting copies of, or links to Apple licensed software outside of Apple legal distribution channels.
I used Yosemite on two different Macs from the day it was released, and applied all updates. Same drill for El Capitan, and I find the latter to be an improvement. If I read, and believed, every frustrated, assertively negative post in the Apple Support community, I might still be using System 9, or DOS. These are not however, the reviews that you should be reading, which in most part, are positive.