Is this an error with new software? + Reverting back to an old version


My first layers were not as good lately and I noticed when adding an object there is a small gap between the virtual build plate and bottom of object, this is on a fresh install of the latest version ( with no settings changed on windows pc.......Is this normal?

Also I wanted to install an old version of the software to compare it but when I unistalled the latest version and tried to install an old one it would not complete the installation no matter what version i used, is it possible to downgrade.

many thanksĀ 

everytime you install the software it will erase the existing one. The small gap does not actually exist when printed, dont worry.