Does SG9 apply to the skills match? I understand that the rulebook says all rules of the tournament (besides mobile goal and zone color) apply, but since the purpose of SG9 is to prevent hoarding, I wondered if maybe it was different in skills.
To directly answer your question, yes, SG9 still applies in Skills Challenge matches. Robots may still never Possess more than one Cone at a time, Robots may still interact with Cones that are fully nested on upright Goals without those Cones counting towards the possession limit, etc.
That said, the hoarding portion of Note 1 specifically refers to keeping Cones away from an opposing alliance. Since there are no opposing alliances, then this specific portion would never come into play in a Skills match, in the same way that SG4 (the Pinning/Trapping rule) would never come into play.