Q1 Why does some of the geocache icons have a sunburst in the upper right hand corner?
The caches that were most-recently imported are automatically assigned the "new" tag, which puts a sunburst on the cache icon. The "new" tag is automatically removed the next time you Sync (import). Alternatively, you can do as I do and immediately select "Clear all 'new'" when sync has finished.
Q2 The GPX files have cache attributes (kid friendly, poisonous plants, etc) but they are not displayed in the details on GeoHunter.
Hmm, I never even noticed. I don't pay attention to cache attributes since most of the time they are frivolous anyway.