To determine how many of the given rows are correctly matched, we need to verify the information provided for each art form based on historical and cultural context. Let's examine each row:

1. Mohiniyattam:
   • Origin/Community Associated: It is indeed associated with Chera patronage from the 9th to 12th century CE as it is a classical dance form from Kerala, which was historically under Chera rule.
   • Key Feature: Mohiniyattam is characterized by graceful swaying movements and has links to the Mohini incarnation of Vishnu. This information is correct.
   Therefore, the information in this row is correctly matched.
2. Thullal:
   • Origin/Community Associated: Thullal was indeed introduced by Kunchan Nambiar.
   • Key Feature: It is a solo satirical dance form performed during temple festivals. This description is accurate.
   Thus, this row is also correctly matched.
3. Kutiyattam:
   • Origin/Community Associated: Kutiyattam is traditionally performed by the Chakyar community, often along with the Nambiar drummers.
   • Key Feature: It is a Sanskrit theater and performances can indeed last from six to twenty days.
   Therefore, this row is not incorrectly matched.

After examining the details, it becomes clear that two rows are correctly matched, and they are related to Mohiniyattam and Thullal. Kutiyattam's key feature aligns with the description; however, the community specification could require more cultural detailing.

Hence, the correct answer is: Only two.