Closing voucher at end of fiscal year


After spending quite a lot of time familiarising myself with ERPNext, I started a few weeks
ago to re-enter all my data into my ERPNext system. The reason I did not simply
restore from backup is that I discovered to many data-entry errors from the previous system.

Anyway, so ai am entering data from 2019 as well.

My question…
I have progressed past the first year-date without closing off. So there is data in the system
from 2019-2020 FY as well as 2020-2021 FY. I di dnot close off at the end of 2019-2020 FY.

Is it still posible to close off the previous FY even though I have data for the next year
already entered ? Is this going to break anything ?

What is the benefit of closing off because I can look at an account and simply set filter
dates to get the enteries fro that particular year ?

Please be patient with these questions because I am not an accountant !!!