Is iMac 2014 updated for Big Sur?

Check in the About this Mac from the Apple logo on top left of the computer

Exactly what does it show

Provide a Screen Shot without the Serial number showing and post that image in a reply

please see P. Phillips' reply to see if you have Big Sur.

but if you are asking if a 2014 iMac can be upgraded to Big Sur, then yes, that iMac is compatible.

Now if the question from @jefferythefrog in above is really what your meant.

Please, if there any credit from below really belongs to @jefferythefrog for pickup up on this

The Age of this computer will Govern what newer version of macOS it will Qualify to install. 

Use About this Mac from the Apple Icon on Desktop - the required Information will be there.

With the above information in-hand - follow this How to get old versions of macOS and verify what version this computer Qualifies to install.  For Best results use Safari to commence the download as Others may not work.

Safari will open a redirect and open the Apple Store where the download can commence.

Does this computer appear as Listed and qualifying for an upGrade to a newer version of macOS ? 

If Yes, suggest having at least 50 GB of Empty Space on the drive.

It will allow the Full Version ( about 12.xx GB ) to download, expand and then commence to install.

If there is Third Party Security Software installed - remove it.

It will interfere with both the download and installation process.

The below link will help identify which version of macOS  this computer may Qualify to run.

macOS Big Sur 11 hardware requirements

Make Time Machine Backup  is very useful 

Notation - Mojave is the Last version to support 32 bit applications / extensions and Drivers. Catalina, Big Sur, Monterey, Ventura supports only 64 bit and there is no workaround.

Suggest using Go64 to find 32 bit application before attempting the upGrade. Some or many of the Application already installed may require an update or upGrades to 64 Bit Version