I'd go for MrFist, but it's still personal preference of course.
Dude
A gold geodude is just a shiny geodude you must keep finding geodude in granite cave until its shiny.
Geodude evolves at lv. 25.
Geodude evolves beginning at level 25.
Geodude evolves into graveler at level 25.
Dude
What you have encountered is a shiny Geodude, which, as you described, is gold and a normal Geodude is a light gray color. Think of shiny Geodude as a gold nugget and a normal Geodude has a regular rock.
Geodude will evolve into Graveler.
No, Geodude is not a real creature. Geodude is a fictional character only in the Pokemon franchise.
A gold geodude is just a shiny geodude you must keep finding geodude in granite cave until its shiny.
geodude evolves at lvl 25.
No, trading a Geodude into the Alola region will not cause it to evolve into Alolan Geodude. To obtain Alolan Geodude, you must catch it in the Alola region, as it has a different regional form. However, if you have a regular Geodude, you can evolve it into Golem, but it will remain the original form.
A female Geodude can be found randomly in the wild. A Geodude has a 50% chance of being female.
If you like 'Nan' as a nickname, then yes, it is a good nickname.
There are three Pokemon in the Geodude evolutionary line - Geodude, Graveler, and Golem. Geodude evolves to Graveler at level 25, and Graveler evolves to Goiem by being traded.
geodude learns rockthrow at lv. 11
Geodude has a mouth and apparently it can shoot flames.