gate here?

The desert line is apparently disused, and blocked by rockfall.
If you know which sections are still in operation and which are disused, here is the correct way for tagging: osm.wiki/OpenRailwayMap/Tagging#Tracks

Hokuriku shinkansen should be there

name=Ashikaga Halal Food
osm.org/node/4409459364

shop=market ? Is it an entire marketplace? ( osm.wiki/Tag:amenity%3Dmarketplace ) Specific shop (see osm.wiki/Key:shop for possible values) ? Something else?

"場所違う"
The place has gone or never existed. This is an auto-generated note from MAPS.ME application: a user reports a POI that is visible on a map (which can be outdated), but cannot be found on the ground.
POI name: ガトーフェスタハラダ本社工場
POI types: shop-confectionery
OSM data version: 2018-02-09T21:26:02Z
#mapsme

osm.org/way/980919411/history

is this retaining wall really made out of soil?

osm.org/way/981635940/history

is this retaining wall really made out of soil?

"少なくとも、50号から見える範囲では開通してる。"
POI has no name
POI types: highway-construction
OSM data version: 2018-03-16T17:06:02Z
#mapsme

旧花輪小学校記念館

アグリの森