What is the principal distinction between لَنْ يُفْعَلَ and لَنْ يَفْعَلَ?

Negating the Imperfect with Lan and Lam: Subjunctive, Jussive and Full Paradigms

• The first is passive, the second active
• The first is perfect, the second imperfect
• The first is dual, the second plural
• The first is imperative, the second prohibition