This the one and only correct command for syncing with the repo mirror.
If you know your system is up-to-date but you need a single applicaton you can use
sudo pacman -S <pkgname>
It is possible to flash android phones.
sudo pacman -S android-tools
For Samsung phones you may need heimdall
sudo pacman -S heimdall
Add your user to group adbusers (remember to logout to make the new group stick)
sudo gpasswd -a $USER adbusers