Hi Rene,
Hope this helps .....
1. The colour of anti freeze is a dye and cannot be used to determine type.
2. My 2006 built 1.8 Duratec handbook clearly states Morris ethylene glycol anti freeze (the up to date Morris product called "MEG" ......monoethylene glycol). It's standard stuff. My handbook also covers the Plus 4 specifying same antifreeze.
3. I believe g48 and g12 are both ethylene glycol based but please do your own research to determine suitability. I stick to the book where possible.
4. I would suspect the white substance is limescale or formed solids due to low mileage and/or a poor coolant change regime (no criticism meant). You can't get very far into the tank so limescale remover might help (obviously take tank off car!).
5. The tanks are from Ford Focus RS MK1. There are two types very similar.
6. Notwithstanding what you use flush out all old coolant, a really, really good flush and replace.
7. If any doubt maybe your local friendly garage can give an opinion.