I am seeing both blender 2.8 and blender 2.81 in my program list. So can I uninstall blender 2.8? I have previously installed Blender 2.8 and today I have updated to Blender 2.81 by downloading and installing it from blender website. I see 2 blender programs in program list, one Blender 2.8 and Blender 2.81 which seems awkward. I thought it would rewrite the previous version which I already have but instead it creates a new blender program, although the desktop icon is still single and refers to Blender 2.81

So can I uninstall Blender 2.8 without uninstalling whole blender?
And is Blender 2.8 taking extra unwanted space in my hard drive?
and
How to update Blender the right way efficiently?
Can I update Blender without downloading the whole software again?
You can uninstall 2.8. Every version of Blender doesn't rely on other versions.

Updating Blender is usually done exactly how you're doing it. This is because Blender doesn't automatically update. Sometimes new versions break old files or addons, so it's up to the user to update the program by downloading it. It can be useful in certain cases to have multiple versions installed, although it's rare.

The only way to automatically update that I know of is if you install through Steam, although my understanding is that Steam basically does what you did just in the background.