Learn English – Are there different noun forms of ‘complex’ and ‘complicated?’

Blurry can always be replaced by blurred (except in the word blurry-eyed), but not always vice versa. IMO, blurry, for the most part, fits all three meanings of blurred in the OALD excerpt, not just the first.

However, blurred has another use which blurry doesn't duplicate, and the dictionary doesn't bring out (probably because it's hard to do without examples). When blurred follows is, was, etc., (i.e. the picture was blurred), it can take a modifier or modifier phrase (e.g. the picture was blurred by the rain or the picture was badly blurred). Blurry cannot be used nearly as extensively in this way.

To go into nuances, even in the places where blurry and blurred are interchangeable, blurred suggests a previous state of non-blurriness and may suggest a perpetrator, whereas blurry only reports the state of the object and doesn't connote much more. The distinction is, however, only slightly observed in common usage.

There is no difference in core meaning, and even the connotational penumbrae overlap a lot. It's mostly about the attitude you're trying to convey; and this is going to depend more on each reader's actual experience with the words than with any broad consensus.

Here's how I would use them:

• Diligent if I wanted to express respect and admiration for the worker's application to her project
• Assiduous if I wanted to express respect for the worker's application and thoroughness, while leaving room to doubt the value of her work
• Sedulous if I wanted to acknowledge the worker's application and thoroughness, while leaving room to wonder whether the work might not be better served by insight and imagination

But that's a very personal view; others may feel differently.