Can I use Nordic boots for backcountry skiing in the mountains?

It depends on the terrain. Nordic backcountry or touring boots are suitable for rolling terrain with modest hills where you can descend with a snowplow or step turns. They are NOT suitable for mountain terrain with steep slopes, avalanche risk, or technical descents. For serious backcountry skiing with significant elevation gain and steep descents, you need AT (alpine touring) boots and bindings. Nordic backcountry boots are best for forest roads, frozen lakes, and gentle trails where the primary activity is touring rather than descending.