Hello Stebu,
quite a lot of questions, so ...

I already read something about this from you, but: Locus never resized icons by zoom level or zoom-lock!

Currently, icons from KML are resized only when their size is bigger then 48 x phone DPI (so on big phones is 72px or 96px). In these cases, their size is reduced just to these limits. Sizes small/medium ... are applied only on icons, you define by your own, so icons you selected from default Locus category or own files in Locus.

How to set icon for category you already probably know. Every point in some category have set
a) no icon, in this case take icon from category. When you copy this point, it will then again take icon from new category
b) own defined icon, then this icon go with this point into new category

ad 4) try to export any point with such own icon and you'll see tag in exported file. SO yes, it's possible

ad 5) same as 4. There only not exists list of these icons, but I may prepare some more precise description if you'll want

if you find something not so logical or have any other question, feel free to discuss it. Also are you sure that something has changes? Locus now handle styles completely different then in previous versions, but I hoped that all remain same (for users)

Thanks, Menion!

The "inheritance" of category icon is very useful. Now I do not need to load a *.KMZ file and test if icons are nice (and reload the file with new icon). I only need to load some icons and pick one for the category.

I think this keeps me going for a while :)