I wanna make sure how to use as if and as though. On the internet it is possible to find information about that topic (which I did) but it is not accurate enough.
He acts as if he doesn't do anything wrong
He acts as if he didn't do anything wrong
He acts as if he hasn't done anything wrong
He acts as if he hadn't done anything wrong
As far I know once we start with the present tenses and add "as if" still present but also past tenses will refer to the present, which means that my 2 example isn't about the past but about the present. It just expresses bigger doubts. On the other hand, I heard that we have to use perfect tenses to mark past if starting our sentence with a present verb like my 3 and 4 examples.
Yet, one teacher told me that my 2 example could refer to the past as well, but books and internet sites say it is not true. How do you see that?