iTunes has changed quite a bit in Version 12. I hope this will help you find your way back to the view you liked before.
The mini player button has moved in iTunes 12. Here are two places you can find it.
How to get into and how of full screen has changed in Yosemite. Here is how it works. And here is how to get out of full screen in the apps where the esc is not working.
When you are running on battery power, this setting can really help save energy when you are surfing the internet using Safari.
Here's how to choose what Spotlight returns when you do a search of your computer.