Not Able to Move While in Reverse

yes, transmissions work off of fluid pressure, less fluid....less movement. a transmission doesnt actually use gears...its hydrolic pressure that causes movement

It's possible. How low, just a little or a lot? You need to have adequate fluid level for the trans to operate. If you continue to have problems with your automatic transmission, find a transmission shop or a Geo, Suzuki or GM specialist for diagnosis. If you want to find a specialist, here's a directory link for you: https://repairpal.com/geo-repair-in-sahuarita-arizona