The missile NK recently fired over Japan recently was launched at 5:58 AM. At 6:02 AM the Japanese government sent a text alert. At 6:12 it landed in the ocean. We know about NK missiles launches very quickly after they are fired. I wouldn't be surprised if we know about them before they're fired. This suggests to me that these missiles can be intercepted.
I don't know what kinds of interception technology is deployed in the area, but I would guess there is some and I would also guess that a (hypothetical) NK ICBM would not have significant countermeasures.
I think the real question here is what NK/Kim's aims are. When Iran was actively developing a nuclear capability, it seemed clear that their goal was to get as close to a weapon as possible without actually finishing a weapon. The closer they were, the more bargaining power they had in terms of getting the US/UN to lift sanctions.
With NK, I'm less clear about strategy. In the past, it seemed like NK actions had the aim of extorting aid money from the US/allies. That may still be the case. Here's a chart showing US humanitarian aid to NK since 2001: https://explorer.usaid.gov/cd/PRK