1. When she was young, she had a dream.
2. When young, she had a dream.
3. When being young, she had a dream.
4. Being young, she had a dream.
5. Young, she had a dream.
6. When young, she had dream.
------------------------
Which ones' are grammatical? Are all acceptable in terms of grammar?
1 is the very best. 2 is OK.
All the rest are incorrect.
Out of the six sentences you provided, sentences 1, 2, 4, 5, and 6 are grammatically correct.
1. When she was young, she had a dream. - This sentence is grammatically correct because it uses the correct past tense verb "was" to indicate the time when she was young.
2. When young, she had a dream. - This sentence is also grammatically correct. In this case, "young" is used as an adverbial phrase to describe the time frame when she had a dream.
4. Being young, she had a dream. - This sentence is grammatically correct. In this case, "being young" is used as a gerund phrase functioning as an adverbial clause to express a reason or cause for her having a dream.
5. Young, she had a dream. - This sentence is grammatically correct. Here, "young" is used as an adjective to describe the subject "she."
6. When young, she had dream. - This sentence is almost grammatically correct, but it is missing the article "a" before "dream." The corrected version would be: "When young, she had a dream."
On the other hand, sentence 3 is not grammatically correct. "Being young" cannot be used to start a sentence without additional words or a subject. It would need to be part of a larger sentence, such as "Despite being young, she had a dream."