“Difficult to shoot down” is very relative. Compared to a hypersonic missile, a ballistic missile is very easy to shoot down. 1) it is much slower, and more importantly 2) a ballistic missile follows a parabolic arc once intial targeting (soon after launch) is complete — that is why they are called “ballistic missiles.”

A hypersonic missile (HM) is basically a super fast cruise missile (as in 13x faster) that can carry (IIRC) 3x payload. HMs can change direction and altitude. How well and how often we don’t know yet.

The Russian use of them was to point out that the US has no missile defense system that can handle the HMs.

How many the Russians have is pure speculation.

Certainly the invasion is not going as well as the Russians planned, but so far they have limited their tactics. A brutal dictator like Putin cannot afford to lose this war politically. Using Chechnya, Georgia, and Syria as guidelines he will continue to escalate until Ukraine is basically destroyed. Mariupol is the first example of what Ukrainian cities that do not capitulate will face.

In my (layman’s) reading, Putin will either “win” the war (with massive losses and devastation of Ukraine) or Russia and potentially the world will be destroyed.

Coming full circle: This is exactly why Putin needs an off ramp to exit the conflict with dignity.