Is it 5 o �clock already?
http://www.ldoceonline.com/dictionary/alreadyConcerning your first question. Here �s the quotation of a Grammar:
"There is a strong tendency (
especially in informal, idiomatic English) to use phrasal verbs instead of their one-word equivalents. It would be very unusual, for instance, to say
Enter! instead of
Come in(...)" (page 153 Longman English Grammar by L.G Alexander.
Hope this helps.