2) The gerund form of a verb is also fine with bother. "Don't bother coming home" means "I know you would rather not be here, and I don't want you here either so don't..."
3) I have no idea. I'll guess that it's an amateurish metaphor for eyes.
4) A hide-out is a place to hide from the law, etc. for a long period of time. It is also a verb meaning to use a hide-out. "The bandits went to their hide-out in a cave in the mountains where they hid out all winter.
5) A hairpin turn is a turn (such as on a mountain road) that doubles back on itself. In your sentence it is used as a metaphor for a difficult and abrupt reversal of direction.
6) #1 If I haven't... The thing did not happen. If (since would be better) I haven't seen your sister, then I couldn't have told her about your accident.
#2 If I hadn"t... The thing happened, but I wish that it did not.
#3 There is no significant difference in meaning between "If he didn't think..." and "If he hadn't thought..."
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