According to Michael Swan's Practical English Usage, it is possible to use since without perfect tenses in the main clause, especially in sentences about change. The examples given are:

1. You're looking much better since your operation.

2. She doesn't come round to see us so much since her marriage.

3. Since last Sunday I can't stop thinking about you.

4. Things weren't going so well since Father's illness

I'm unable to understand this rule well enough. What about these sentences:

I'm living at my friend's house since last Sunday. (= I lived somewhere else before Sunday but now I live with my friend, which is a change).

Since coming to London, I play a lot of Cricket (I didn't play much Cricket before coming to London but now I play a lot).

I know her since last year (I didn't know her before last year but now I do).

Are these sentences also correct?