so inside the trichomes
Geranyl pyrophosphate and a precursor to olivetolic acid react, a c12 (for pentyl) c10(for propyl)polyketide,catalysed by an enzyme to produce cannabigerolic acid,. The production of Thc (and propyl)thcv cbd cbdv and cbc cbcv are controlled by 3 different enzymes Thca synthase being the enzyme converting cbga to thc through an oxidative cyclization of the geranyl group on cbga(of course this is a bit simplified for y'all) geranyl diphosphate + olivetolate =cannabigerolate + diphosphate.. cannabigerolate + O(2) = Delta(9)-tetrahydrocannabinolate + H(2)O(2)
The plant has trichomes throughout its stages of life, yes the outer waxy layer will be in higher proportion. But hash oil can be made fabulously. The cannabinoids don't develop at different stages at different times.. Some however are much more stable in heat and light. Like cbd for example. An early harvested plant often can smell perfumey soapy and even "green" from corresponding aldehydes and ketones, this will dissapear in the cure with cyclization of those aromatic compounds.
The trichomes turn amber from the rapidly degrading thc and other terpenes (altering that smell) we can so this with a bad batch of hash oil too. Throw it under the hps for 45min and have a beautiful bright red extract
Also I should note, THC largely breaks down into delta 8 etc. Cbn is not a direct product of degradation, quantities rise in freezing conditions unrelated to THC content. Its An enzymatic process. Though it is rapidly formed over about 400°f
