Android versions

Android version 4.2 6.0 9.0 Notes
RAM 340M1 424M2 512M3 It also depends on the display resolution and size:
On android 9, it can go up to 1824MB on 64bit ARM with very high dpi and resolutions
/data partition 4 GB It might also be possible to use external storage for that

1 android-4.2-cdd.pdf

2 android-6.0-cdd.pdf

3 android-9-cdd.pdf and html version

Android 9.0 compatibility

Device RAM Display
Samsung Galaxy SII (i9100) OK:
* Has 1GB and an HDPI display9
* 512M required for 280dpi or lower on small/normal screens*
HDPI1: 480x800 233 ppi9
Samsung Galaxy SIII (i9300) OK:
* Has 1GB
* 608MB required for XDPI
XDPI1: 720×1280 306ppi2
Samsung Galaxy SIII 4G (i9305) OK:
* Has 2GB
* 608MB required for XDPI
Goldelico GTA04 A3 May be or may not be OK:
* The A34 and A45 have 512MB of RAM
* 608MB required for xdpi but the resolution is very small
XDPI1: 480×640 282ppi2
Goldelico GTA04 A4
Goldelico GTA04 A5 OK?:
* The A56 may have 1G of RAM
* 608MB required for xdpi
LG Optimus black (p970) OK:
* 512M
* small screens with 280dpi or less
HDPI1: 480×800 233ppi3
Amazon Kindle Fire first generation OK:
* 512M7
* mdpi or lower on large screens
mdpi: 1024×600 at 169 ppi8

1 https://en.wikipedia.org/wiki/Pixel_density#Named_pixel_densities

2 https://en.wikipedia.org/wiki/Galaxy_SIII

3 https://en.wikipedia.org/wiki/LG_Optimus_Black

4 http://projects.goldelico.com/p/gta04-main/downloads/get/GTA04A3-1-complete.pdf

5 http://projects.goldelico.com/p/gta04-main/downloads/get/GTA04A4-3_System_Manual_Complete.pdf

6 http://git.goldelico.com/?p=letux-uboot.git;a=blob;f=board/goldelico/letux-gta04/gta04.c;h=258b2be62904d98639a9a92afc2ede793685eb4c;hb=refs/heads/master#l228

7 https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/omap4-kc1.dts#n16

8 https://en.wikipedia.org/wiki/Kindle_Fire

9 https://en.wikipedia.org/wiki/Galaxy_S

Source code and configuration

Android can be configured to use less hardware resources. Here are some links on the topic: