Lord Vishwakarma is the divine creator, and the main reason behind paying homage is to seek blessings for all creations that we regularly do in our lives.
Indira Ekadashi falls in the Krishna Paksha of Ashwin month. The previous day you must perform a Shradh for your father and observe a fast on the next day of Ekadashi.
As per Hindu beliefs, Sankranti is when the Sun transitions from one zodiac sign to another. So, when Sun goes into the Virgo sign, it is called Kanya Sankranti or Ashwin Sankranti.