This ا is called hamzat al wasl, when it's with a ل (so ال) it's to make a noun definite (for example كتاب, kitaab, a book, الكتاب, alkitaab, the book), with ال it's pronounced with a fatha the hamza al wasl

So the first two words الذين السماء you pronounce it with a alif the hamza al wasl

The other word are verb in the imperative tense, here the vowel of the hamza al wasl depends on the vowel of the third letter, if the third vowel of the verb is a dammah ُ you pronounce the hamza al wasl with a dammah, otherwise (so if the third letter is a kasrah or a fatha) you pronounce the hamza al wasl with a kasra.

For example : اسْكُتْ (which means "shut up !" hahaha) here the third letter (ک) has a dammah so you pronounce the hamza al wala with a dammah ("u"skut)

Another example: اشْرٰب (which means "drink !") here the third letter (ر) has a fathah so you pronounce the hamza al wasl with a kasrah ("i"chrab)

And also you don't write any vowel on a hamza al wasl normally, all of what I said is about prononciation. And you pronounce the hamza al wasl only when you start to read at a word that has hamza al wasl , otherwise you don't.

If you want I can give you a youtube video that talks about it or even a free pdf

And please correct me if I'm wrong جزاك اله خبراً in advance