YES.  Even if your account request has been approved, you need permissions to edit any information about a team - including general information, rosters, schedules, etc.

If you need access to edit data, please notify the league and provide your name, team and what your role n that team is.

Absolutely!  Each user is capable of being assigned to any number of teams.  There really is no restrictions.

No.  The SWIBL website is really for use by coaches and league administrators.  Parents really do not have a need to log into the website.  Only those individuals who are editing content (e.g. rosters, game scores, etc.) need an account.