Smooth, although I'm more a fan of whollistic/bespoke compliments personally e.g. about her as a person/girl, or some aspect of your conversation that stands out in your mind
Sure, why not? I wouldn't mix it up with the applications process though, I'd make it reasonably clear from the outset that you'd like to get to know more about
her not (just) the job!
I wouldn't ask for a girl's number unless I felt she was likely to give me her personal one e.g. we had established rapport, and ideally I'd seen some IOIs, and was prepared to say something like
"this is your personal number, right?" with a cheeky grin on my face (she can only say no, big deals)
Correctamundo
Haha, bless!
The most sophisticated way is to demonstrate solid social skills and not a hint of desperation e.g. talk naturally, talk about her, make assumptions about her, challenge her, subtly invite her to question you (on a personal level), use strong non-verbal communication/body language, demonstrate self confidence and conviction, and then ask for her details as if it's no big deal. Better yet, just tell her you’d like to see her again, and let her suggest you should get her number or something