Garage Band not working correctly

Hello everyone, Long story short I have a Late 2008 Macbook Aluminum and I upgraded it to Yosemite in October. The performance went down the hill with the upgrade. So I recently went to downgrade the computer to Mountain Lion. I needed Garage band for a media production class that I am in, so I went to download it from the App Store where I have purchased it. It was incompatible with the version of OS-X that I have. So I got my hands on a copy of ilife 2011 and installed Garage band version 6.0 . However it will not allow me to record my voice, the internal mic is not recognized. In addition to this the timer is not working. So my main question is wether or not Garage Band version 6.0 is compatible with Mountain Lion. If so how can I go about getting a version that works without upgrading to Yosemite. Thanks- Patrick