Many verbs can be both transitive and intransitive.
And I was told there is a semantic difference in the way in each pair (1vs2, 3vs4), would be translated into the same sentences in my mother language(Korean).
What's the difference in the meanings?
In "the glass was broken" and "the door was closed," broken and closed would usually be interpreted as adjectives, not as passive voice verbs. For instance, "the door was closed" typically means that the door was in the state of having been closed, not that someone or something caused it to close.
"The door was opened" is different. The antonym of the adjective "closed" is "open," not "opened," so "the door was opened" is indeed passive voice. "Open" (in one specific sense) is a so-called unaccusative or ergative verb, so "the door was opened" entails that "the door opened." However, even in this sense, there is a subtle difference in meaning: "the door was opened" generally implies that some specific person or thing caused it to open, whereas "the door opened" does not necessarily have that implication.
- The glass broke.
- The glass was broken.
- The door opened/closed.
- The door was opened/closed.
You're not playing with a full deck. How about
Note, first, that open is an adjective, and so is closed, even though it ends in -ed. Opened, however, is not an adjective; it's a verb form. Closed is both an adjective (you find it on the other side of "OPEN" signs) and a verb form. This causes some confusion.
Second, break can be an intransitive (no direct object) inchoative (change-of-state) verb as in (1) indicating something frangible as its subject
Or, like most such intransitive inchoative verbs, break can become a transitive causative verb, meaning to bring about the change in state. This adds an actor subject and takes a frangible object:
And, like every transitive clause, Passive can apply: She broke the glass --> The glass was broken (by her)
But broken can also be an adjective, so broken glass is a common phrase, like open door. But not *broke glass or *opened door. I can't say what distinction might be hard to make in Korean, but all three verbs share their syntax. I suspect it may be the closed/open opposition, which looks wrong from the morphology.
However, in any event "I heard that" is not a good source for grammatical information. Anybody with sufficient nerve can say anything at all about English grammar and somebody will believe it. Don't be so gullible.
(2) The glass was broken.
Standalone, this is ambiguous, the transformative/dynamic (verbal, passive) and the stative (often analysed as adjectival with a converted participle) readings being available:
(2a) The glass was broken by the hail.
(2b) The glass was broken, we were sad to see when we arrived.
.............
(1) The glass broke.
This is obviously a dynamic usage. It is sometimes classed as an ergative usage; the corresponding stative usage, showing a property of the subject referent,
(1z) Glass breaks easily.
is the 'middle voice/usage'.
...................................
(4) The door was opened/closed.
have to be (according to accepted usage) the dynamic meanings. There is almost certainly an implied sentient agent or hydraulic system say doing the opening.
.............
(3) The door opened/closed.
default to the ergative (dynamic, semelfactive = one-off) usage. However, context may indicate the identical-in-form middle (stative / habitual) interpretation:
(3b) The door opened easily before the flood caused it to warp.
