Fairly new user with a brand new problem

Greetings!

Let me start off by apologising if I’ve posted this in the wrong area, and confirming that I did in fact do a few searches first.

I got a Himedia box last year, not 100% sure of the model at the moment but I know that it’s quad core running Kitkat 4.4, and I’ve encountered a new issue that I can’t seem to work around.

Haven’t done too much with it other than set up basic functionality and it’s been working great but started to slow down recently. After a few searches on the interweb I cleared caches and a crap ton of thumbnail jpegs which seemed to make things happier. And then the other day I fired it up and it went straight into Kodi, bypassing what I would assume to be the android title screen, which means I can’t access any of the settings or the Playstore etc.

I can see multiple posts on how to get Kodi to autorun but none to revert to the original state.

And if it isn’t already obvious, I’m a newbie so you might want to keep any explanations simple, like you were talking to a house plant.

Thanks!