6 levels make use of the following potential new skills: slider, grenader and spearer. You need the latest Experimental Build (V6) for this.

That sounds very risky, in my opinion. Especially in a pack with only 22 levels, 6 being dependent on whatever the current experimental version looks like is a huge number.
namida said for good reason that we shouldn't make any packs relying on experimental versions. It's precisely for this reason that I've halted the development of all of my packs that are planned to rely on whatever the final new skills will be. Some of the test levels I made for the experimental version are indeed intended to become part of packs later, but none of that is official at this point.
Furthermore, namida also said the experimental version will stop working in July this year. And that any packs relying on experimental versions to be playable will be deleted from the forums at that point.