Some curious valve differences

[Menace_AO]

Okay, gang, time for some valve schooling for yours truly.

Can someone explain to me the reason for the following differences in the following valves:

1. Mistaken question, withdrawn.
2. Mistaken question, withdrawn.
3. If, as Tuna says, the reg spring packs in the classic valves never wear out, why did AGD elect to go with a dual counter-wound spring system in the RT-style valves? Answered!
4. Related to #3, do these dual counter-wound springs ever wear out? Answered!
5. Why do the RT (classic) and ReTro (and some E-Mag?) valves have only the single o-ring hole milled in the on/off well rather than being completely bored out like the earlier Classic and later X-valves? Also, is it in fact true that some E-mag valves have only the single o-ring hole? Answered!
6. Why is the reg/valve body threading on all RT-type valves different from that of the classic valves? Answered!
7. Is the back cap of the RT-style valves stainless? If so, what prevents it from wearing the ano on the reg body during adjustment? Answered!
8. Did later versions of the ReTro valve move to the double o-ring well after the fashion of the later E-mag valves?
9. Did all, some, or none of the RT Pro valves have the double o-ring well?

Thanks very kindly!