... using newest availabe firmware. How can I do that?

I bought my N900 2nd hand, and for example - in Application Manager there was 'search' function. I didn't like the general mess in the phone, so I 'reflashed' everything using tutorial I found on the internet. Everything is fine, but I have my doubts if its the newest availabe version.. There is no "more..." in the menu as well.

About says:
Maemo 5
Version: 20.2010.36-2

I don't have any important data on my phone now, so installing everything from scratch would not be a problem for me.

Thanks in advance!

PS. I bought my Nokia in Netherlands.