[Grammar] Adjective or Verb with -ed in present tense

[need help]

FIrst of all, I am still learning this language.
I keep run into problems using "ed".
when I read in reading materials, I found a lot of using "ed" but it is in the form of present tense.(or i make a mistake )

I see sentence like :

1. Specially formulated for very dry skin.
2. It can be used on any ......
3. Subsidised optional 2-week study tour to the Netherlands.
4. Courses approved by Ministry of Higher Education and accredited by .....
5. Well balanced curriculum to ensure effective coverage of maritime knowledge and skills.
6. The explanaitions of grammar points are backed up with clearly focused exercises.

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Sometime even though I write or read a paper in present tense, there are some verb that ending in -ed. I dont' get it! Can anyone give me a clue and explainaitions about all of this ..?

 

[5jj]

The third form (past participle) of the verb is used in the passive mood in all tenses:

It is used / It was used /It has been used / It will be used / It is being used.

It is also frequent used as an adjective: a used car.

 

[need help]

Sir,I just want to ask you abaout the sentence that I provided,
can you tell me from no 1 to 6 whether it is adjective 'ed ', passive mood or past tense . All of this seem same and I cant figure it out .
Can you give a explaination about the problem ?