How is LH hormone produced? Is it necessary to have a growing follicle to have an LH surge? How often does ovulation occur after a positive OPK?

LH. LH is made in the anterior pituitary, it takes a whole book chapter to explain how. It is necessary to have a threshold Estradiol level to have an LH surge, so practically speaking it is necessary to have a follicle. It is unknown for certain how often ovulation occurs after surge, but conservatively it is likely at least 95% of the time.