I'm not a teacher..;

;
anyway, these days I've studied about 'as if.'
however, I can find only little information about it .
I just have several questions.
1. 'as if' can be used at the beginning of the sentence? (especially, in the conditional sentence)
"As if" generally does not begin a sentence. However, you will hear it used colloquially either by itself, or to introduce a partial sentence, as a reply. A: "John said that you are not very clever." B: "As if he'd know!" This means "He says it as if he would know. But he obviously doesn't".
like 'as if she knew everything, she acts.'
is it possible to use?
No. You must say, "She acts as if she knows everything."
2. I've thought 'as if clause' is an adverbial clause. then, it should be used after
(or before?? if first question can be revealed to be okay)
No, it's not OK.
a perfect sentence? I mean, the sentence that is needless to be added to 'clause or something else.'
Sorry, I don't quite understand this.
3. after 'as if' (as it is for a conditional sentence) can I use would/ is doing(for future tense) / might/ will ?
in indicative sentences, I think, it is possible, am I right?
I'm not sure. Could you write a sentence as an example of what you mean?
please

let me know in future tense, how I can use 'as if' , deviding it into two moods( indicative & subjunctive).
"He's going to join the army (future), as if he had (subj) the strength or agressiveness to do that!"
and please give me some examples of each of them.
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plz ㅠㅠ