Learn English – the difference between “super” and “superb”

There is no such English word as "scientifical." You might make an argument that "acoustic" has the same meaning as "acoustical," though. Ain't English great?

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.