Table: football_league_champ_managers_2
Columns: team
outgoing_manager
manner_of_departure
date_of_vacancy
replaced_by
date_of_appointment
position_in_table

Question: Who came as a replacement in Sheffield United?
SQL: SELECT "replaced_by" FROM football_league_champ_managers_2 WHERE "team" = 'Sheffield United'

Question: When was the new manager of the team on 21st position appointed?
SQL: SELECT "date_of_appointment" FROM football_league_champ_managers_2 WHERE "position_in_table" = '21st'

Question: What was Gary Megson's manner of departure?
SQL: SELECT "manner_of_departure" FROM football_league_champ_managers_2 WHERE "outgoing_manager" = 'Gary Megson'

Question: When did the old manager vacate his position in Plymouth Argyle?
SQL: SELECT "date_of_vacancy" FROM football_league_champ_managers_2 WHERE "team" = 'Plymouth Argyle'