No it’s not a late 2012, defo can’t be updated anymore unfortunately
Yours should support Mojave just fine if it’s a “Late 2012” model. It’s on Apple’s supported hardware list. The bigger question is why would you want to upgrade to Mojave? For me Mojave (and its default APFS format for SSDs) is a pain, especially as DiskWarrior can’t currently repair APFS volumes. People often think latest is best but this isn’t always the case, particularly with regard to older hardware, and if your setup works for you right now my advice is don’t update simply for the sake of it.
Yep, depending what version hardware. Not too bad so long as your BT and WiFi is supported. Biggest issue seems to be graphics and dark mode.
Lots of known issues
For those with unsupported Mojave Macs you might try this: http://dosdude1.com/mojave/ Could be a pain when updates come out though.