Regarding highlighting / lighting up objects on mouse-over:
There are many ways to achieve this, using Spine or Unity.
Since there are many ways to highlight an object, what exactly do you have in mind by "light up" - shall it get brighter alltogether? Or shall it receive an outline as well? Shall it slightly grow in size?
You can do many of these things with Spine or the Spine-Unity runtime: e.g. change the slot's color to something brighter (in an animation in Spine, or programmatically using the Spine-Unity runtime), switch attachments at a slot from a normal to a hightlighted version, etc.
Regarding blurring backgrounds:
I don't know if this applies in your situation, but you could use a depth of field (DoF) camera effect to focus on e.g. a character's head (set focus depth to this object) and blur things that are further away from the focus plane. This way you could adaptively fade blur in and out and have nice transitions.
A shader will always be involved when applying blur on a normal image or scene.
You could of course also pre-process your images and apply blur in photoshop and then quickly swap images, but that way you will not get smooth blur transitions.