A "pure " adjective is this: The red house is on the corner. ( red) He is a good man (good) it is a different kind of adjective that is formed by adding "ly" meaning "in a way that is ..." He speedily drove the car down the road. He angrily slammed the door. He happily went about his work. Suprisingly he didnt know what he was doing. Then by adding "y" or already ending with "y" or using the pp we have a thing that is: This car is speedy. The terrain is varied. Her heart is broken-- She has a broken heart. He is happy. He was suprised he knew exactly what to do. we can see in the last example the past particple is used, just as it is used to form perfect tenses and passive tenses : They had suprised their children with a present. (past perfect) They had been suprised many times (passive past perfect) They were suprised by the news.( passive past)

They're adjectives derived from a verb. As a general rule, you can use the past participle of a verb as an adjective, and its meaning is similar to what it would mean in the passive voice. E.g. "The window is broken." - "Broken" is considered an adjective here, but the meaning doesn't change if you consider this sentence to in the pasive voice. In a sentence like "I see a broken window", "broken" can only be considered an adjective. Whenever you see an adjective ending in "en" or "ed", you should check to see if it's derived from a verb, and then you can figure out exactly what it means e.g. annoyed, bored, excited, forgotten, fallen, mistaken etc. Adjectives that describe people or things doing something are derived from the continuous forms of verbs. "It is interesting." - It doesn't matter if you consider "interesting" an adjective or if you consider this sentence to be in the present continuous, the meaning is the same. "Interesting" can only be considered an adjective in sentences like "The interesting story...".

Yes, they are. Don't sound like a broken record! ;) Some dictionaries show it as a participle first, others show it as an adjective first.

You should look at my answer Hamed, I answered your question.