Which previous course rule required the most important correction in this level?

When Congregation Begins during an Individual Fard or Sunnah Prayer

• The claim that after the first Sajdah of Fajr or Maghrib the individual prayer should always be completed.
• The rule that Zuhr has four Fard rak'ahs.
• The rule that congregation has a prayer leader.
• The rule that prayer includes Sujud.