I am considering buying a Samsung Galaxy phone. Is there an option (either basic phone function or a third party app) which provides a keyboard in alpha sequence, that is ABC layout instead of QWERTY?
There is a keyboard available that is on the app store, it is designed for dyslexics who have difficulty in recognizing the letters, the problem with the QWERTY layout is that dyslexics cannot "see" the letters and looking all over the keyboard for it, have a mate who suffers from it, and this was born out of the idea when I watched him struggle with the touch keyboard.
This keyboard is actually from stock AOSP Gingerbread source, with letters re-arranged into ABC layout.
It is available here on Play store.
Edit: Disclosure, I am the person responsible for the aforementioned app.
The stock, AOSP Android keyboard does not have the ABC 'old fashioned' keyboard layout, however some manufacturers package their own IME (keyboard), that comes with this feature.
Some manufactures are LG, and Sony Ericsson that do this (Sony Ericsson Xperia devices do).
AFAIK the stock Samsung IME doesn't come with this option - however, you can download 3rd-party IME's that have this layout format.
I published an alphabetical keyboard that's now available on Google Play and Androidfreeware.net.