Is it permissible to begin an Islamic lesson with the stated formula that includes the Basmalah, the Hamdalah, prayers upon the Prophet, and supplication?

The words mentioned are good, and there is no harm in beginning lessons and sermons with them. However, if the preacher fears that people might believe it is a Sunnah from the Prophet, peace and blessings be upon him, then he should sometimes use other phrases to dispel this misconception. The best approach is to start sermons and lessons with the Khutbat al-Hajah (Sermon of Need) which is authentically reported from the Prophet, peace and blessings be upon him.