Yes, they are OK. The second sentence is even poetic. The first, though correct, sounds less beautiful to me. Both of your sentences could be greatly improved by adding an expressive verb. The only verb you use is "are". That is an important verb, to be sure, perhaps the most important verb in English. But it is not a powerful verb. It doesn't express anything. It is boring. Bring your sentences to life by using expressive verbs: Her lovely dimples sparkled around a meek mouth on her round face. Her eyes shone bright and clear, like an autumn sky. For an extra touch, you can jazz up your expressive verb with an adverb: "Her lovely dimples sparkled gracefully"

Yes, it's fine. It sounds very native level. It's quite poetic.

To me, it’s not clear at all because I don’t associate any characteristic with ‘the autumn sky’. If, however, the people you are talking to DO have such an association, it could be fine. Moreover, we usually use the words ‘bright’ and ‘clear’ with eyes in certain figurative expressions. To be ‘bright-eyed’ is to be interested or eager, and to be ‘clear-eyed’ means to see things realistically or precisely, and, used that way, are even somewhat contradictory. You seem to be talking about the eyes having an attractive appearance - there are many better adjectives to convey that meaning.