Does anyone know if opening the butterfy jars give xp? I think I saw it gives it to the lowest skills, and if this is true can it be shut off? I am a Classic lvl 3 skiller with 9hp and want to stay that way.
Yes, when you open a butterfly jar (possible reward from the Mysterious Egg) you will gain xp in your lowest skill, just like catching a Guthixian butterfly.
You can toggle the xp off by speaking to Orla Fairweather, found west of the Lumbridge crater, and at the Memorial to Guthix.