I want to ask you when we use the form 'should' instead of 'if' in sentence like this:
a) "Should you send me a mail and get nothing back in 24 hours, make sure to use other means of communication to confirm that I received your message."
b) "Shops are open, should you be in need of something to drink."
Is it common or formal form? When can I use it? And why in the second sentence somebody hasn't written "should you are in need (...)", like he could in "if you are in need (...)"?
And additionally – which form is better:
1) I have got a question about...
2) I have a question about...
3) I got a question about...