1. Names and labeling rules are in default style. They are follows http://www.mapcss.org/ specification with some extras.

2. Markers could be added via GLImage or GeoJSON with custom style but I've also have some difficulties here, and can't support you with working example.

So the best way is to ask getyourmap dev. team.

1. Names and labeling rules are in default style. They are follows http://www.mapcss.org/ specification with some extras.

Open DefaultStyle.bundle/Style.mapcss most of the names marked as

{ 
  ...
  text:eval(locTag('name')); 
  ...
}

You could use

text:eval(any(tag('name:en'), tag('name'))); 

In that case, name:en will be used for names first, and if there is no name:en, name will take it's place.

2. Markers could be added via GLImage or GeoJSON with custom style but I've also have some difficulties here, and can't support you with working example.

So the best way is to ask getyourmap dev. team.