Can the Imam offer the Salat (prayer) with only those who are present (for the prayer)? And can be deliver a Khutba (religious talk) on Friday if it is raining?

Narrated Anas bin Seereen: I heard Anas saying, "A man from Ansar said to the Prophet, 'I cannot pray with you (in congregation).' He was a very fat man and he prepared a meal for the Prophet (ﷺ) and invited him to his house. He spread out a mat for the Prophet, and washed one of its sides with water, and the Prophet (ﷺ) prayed two rak`at on it." A man from the family of Al-Jaruid [??] asked, "Did the Prophet (ﷺ) used to pray the Duha (forenoon) prayer?" Anas said, "I did not see him praying the Duha prayer except on that day."