How to update the OS

[deedend]

sudo pacman -Syu

will update all of the system packages

Sorry but, is this the same as reflashing to a new version? Apologies if my question is silly

sudo pacman -Syu is the same as apt upgrade
sudo pacman -Syyu is the same as apt dist-upgrade

Neither will erase what you have on the phone. So, no, not the same as flashing a new OS, just upgrading the one you've got.

OK thanks, that's explain a lot for an unexperienced debian old fart like me, but what I mean is, is the result in terms of features the same as reflashing the whole thing? Or is it always advisable to perform a full flash to have the very last version?