"what different between on form 7202 for 2021 PART I LINE 2 DOT 3 AND PART II LINE 25a is"

Two different types of leave credits.

Part I is an Extension of the refundable qualified sick leave.

Part II is a New family leave equivalent credit.

Also, Part II has only that one qualification. Part I is not as restrictive. They both apply between January 1, 2021, and March 31, 2021. That means the maximum of the 60 days have to fall in that 90-day window.

I found a nice reference document:

https://www.abetterbalance.org/wp-content/uploads/2020/04/SelfEmployedTaxCreditFactSheetJan2021-1.pd...