Hey Growmie...
You can actually defoliate in veg and flower. In veg, you would defoliate to make sure the plant isn't getting too bushy so the lower branches can also get light. As far as when to lollipop, it should be done in the early stage of say week 1 or 2 so you don't cause any stress on the plant and to prevent those popcorn buds from growing.
Hopefully, this was helpful and remember ..."Happy Growing" and "Free your mind one puff at a time".
Mr_Weeds_Autos