Changing the fiscal year End date

Hi there,
1.
We have set the fiscal year end date which is Jan
Our accounting works are following the canlendar date
As our company registered in Nov.2021, and we are preparing tax return of 2022.
What if we changed the fiscal year end date to Nov, what would be caused

2. What is the difference between those two

First month of fiscal year

First month of income tax year

Best,