my ipad states is is uptodate with ios 12.5.4 but this is not the latest version available, any ideas why?

The first generation iPad Air, iPad mini2 and mini3 can only be updated to iOS 12.5.4.

Apple ended major update support for these models of iPad in September 2019 - although they since continue to receive “point” security updates - the most recent being released just a few weeks go. These devices cannot be updated to iPadOS 13 (or any later major versions of iPadOS) as the internal hardware does not meet the minimum technical requirements (CPU and RAM) for newer versions of iOS/iPadOS.

Some App developers have dropped support for iOS versions preceding iOS 13.x for technical reasons (often because APIs or software libraries upon which they rely have been updated in the new version of iPadOS, making their App incompatible with earlier versions). 

Whilst many App titles remain compatible with your iPad, if you want or need to access to Apps requiring the most recent versions of iOS, you’ll need to consider replacement of your iPad with a newer or current model that supports iPadOS14.

Sorry, I appreciate that this may not be what you were hoping to learn.

I hope this information provides helpful clarity as to your available options - and the limitations of your existing iPad.

Installing Norton 360 on your iPad [arguably] adds precisely no protection to your iPad.

There are no true Anti Virus protection products available for iOS/iPadOS. Those that claim to do so are little more than a placebo. Due to the sandboxed architecture of iOS/iPadOS, Apps can only access data in their own [segregated] application data store; as such, an AV product cannot access the system or other Apps data - necessary for any kind of AV scanning or malware protection.

As for updating your iPad, Apple are still updating your iPad within its technical capabilities; as already described, your iPad does not have the necessary resources to run iPadOS13 or later.