Do I need to update every update or can I skip to Big Sur?

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

Tips Big Sir Upgrade Released Nov 2020

Empty Space Requirements specific to the Big Sur. Apple states 35.6 GB Empty Space but suggest 50 GB

Make Time Machine Backup  is very useful and can be used to Revert to Previous Working macOS

Notation - Mojave is the Last version to support 32 bit applications / extensions and Drivers. Catalina, Big Sur & Monterey 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 required update or upGrades to 64 Bit Versions.

Are there any AntiVirus, Disk Cleaner, Optimizers, Un-installers, etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal  operation of the OS and may even Corrupt the OS requiring a Reinstallation

You can upgrade directly.

(209317)

Mobilan wrote:

How can you say that antivirus programs are useless. The Mac is just as vulnerable as the lowly Windows platform!

Normally, would not reply to someone other than to the Owner if the Question.

But, since one has addressed an often mistaken impression that macOS " The Mac is just as vulnerable as the lowly Windows platform! "

The above statement is more an impression, not supported with documented evidence and shows a lack of real understanding of how macOS is designed and where its' foundation lie.

There are no known Windows-like Viruses in the wild that self replicate and affect macOS, because of the underling UNIX  Foundation and Permission Limitation. 

Should “ Certain & Specific Software “ referenced from above be installed - it will negatively impact macOS. It is suggested, to download directly from a respected ASC Contributor, the application Malwarebytes for Mac. 

Run the Application and it should remove the malware / adware. That type of software is often times download from Untrusted Sites and / or Untrusted Developers. Even so, this would require the purposeful actions on the part of the User ( you ) to install this software.

Suggest taking the time to read from a very well crafted article and long time Contributor this article The Built in Security.

How can you say that antivirus programs are useless. The Mac is just as vulnerable as the lowly Windows platform!