Can I put iOS 14 on an iPad mini 2?

No, update is not possible.

A first generation iPad Air, iPad mini2 and mini3 can only be updated to iOS 12.5.3.

Apple ended major update support for these models of iPad in September 2019 - although they since continue to receive “point” security updates. 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.

No you cannot. The i pad mini was initially released with iOS 7.0. ... Then, initially with the release of iOS 13, the iPad mini 2 was dropped for update support. The latest version the iPad mini 2 supports is iOS 12.5. 3, released on May 3, 2021.

No, 12 is end of the line

https://en.wikipedia.org/wiki/IPad_Mini#Model_comparison