alexparser

Nope. Needs 3.9 or above.

Login/welcome messages come from the scripts in /etc/update-motd.d, so you can remove/change them as you wish.  If you didn't want the sysinfo, tips,update nofications and armbian-config messages, you can just remove the executable bit (i.e. chmod -x) from the four scripts responsible for those messages (30-sysinfo 35-tips 40-updates 41-armbian-config), and then you'd be left with just the board name. You can also turn that off by disabling the 10-header script. You can also make your own, and have them run and display on login (if properly written and the executable bit is set). 
 
The easiest way to run something before login is to use crontab. i.e. run crontab -e, and then add a new @reboot command for a script that will run after the device has rebooted, and before login.  See this page for some more information and examples. 

Armbian uses old kernels. The build process starts with the ../compile.sh file.  Packages to install is defined in the configuration.sh file.  Additional files are written in the distributions.sh file.

Please also check this for H3 here: http://forum.armbian.com/index.php/topic/1901-patch-for-quick-interrupt-handling-on-the-h3-fast-gpio/ (and please be aware that I've no idea whether/how this could be ported to A20 -- but since H3 devices start at $7.99 currently...)

for the patch to be created & applied properly you have to pay attention to the path
 
example:
--- a/arch/arm/boot/dts/sun4i-a10-cubieboard.dts +++ b/arch/arm/boot/dts/sun4i-a10-cubieboard.dts assuming you have 2 folders (a, b ) and you want to create a patch for the file arch/arm/boot/dts/sun4i-a10-cubieboard.dts
 
you have to "cd" on the higher directory then
 
diff a/arch/arm/boot/dts/sun4i-a10-cubieboard.dts b/arch/arm/boot/dts/sun4i-a10-cubieboard.dts > $HOME/my.patch
 
note: usually the patch command is used with the option "-p1" so ignoring folder a & b when patching
 
of course, you can trick the patch and
diff sun4i-a10-cubieboard.dts.old sun4i-a10-cubieboard.dts.new
then replace the header with
--- a/arch/arm/boot/dts/sun4i-a10-cubieboard.dts +++ b/arch/arm/boot/dts/sun4i-a10-cubieboard.dts --
you may need to read some more piece of info
https://duckduckgo.com/?q=creating+a+patch+with+diff
 
http://stackoverflow.com/questions/23390823/creating-patch-file-for-linux-kernel#23390933
http://linux.byexamples.com/archives/163/how-to-create-patch-file-using-patch-and-diff/

I2S works only in default/legacy (3.4.10x) kernel for now, so you need to install it (or use another Armbian image) to get it working (you still need script.fex tweaks to activate it).