1. Look here - http://www.cic.gc.ca/english/information/offices/apply-where.asp which visa office responsible for your location
2. No clue, other will clarify
3. In your CIC profile, there field appear "this province want to nominate you, will you accept - Yes/No" Make sure you dont confuse answer button due over-excitement
4. Medical is valid for 1 year, so if you think that in a year period from your medical you will cross canadian border - go ahead (for instance you strongly believe in nomination coming soon). About "Where" - here you go, only certified physician can do medical - http://www.cic.gc.ca/pp-md/pp-list.aspx