One of my wild cats (Novus) emerged into 5th instar yesterday with a decurved horn. It was still decurved today, so obviously not snagged or anything:
I trust the horns are purely decorative and this will make no difference.
My youngest (Sextus) turned 4th instar yesterday. I didn't find him early enough in the year to know if he is one of those few that hibernate in 2nd instar.
5m away, on a 2m sapling, Hostilian (5th instar) is outgrowing the leaves: