Afternoon Andrew. Some quick answers as I shoot through on my lunch break.
Can't answer your first question regarding triggers as I get confused in this aspect as well. The answers here take some delving into reference books etc and there are much better versed people here than myself so I'll let someone jump in later on that.
The 34. Well I'll give you may small take on this. I cannot be sure of exact release date but I think from memory the 24/34/36 were released by Diana (just possibly very early ones were stamped Original) as the replacements for other older models within the range. Looking at the 34 in particular I think it was meant to be the BSA meteor of the Diana range in as much as it was a gun for the common man. A mass produced gun- though clearly a few notches up the quality power and accuracy stakes than the meteor. From memory early guns were very plain with no recoil pad or checkering. I think it's gone on to be a best seller for Diana and over that time I think (or it seems to me at least) that it has undergone a number of facelifts commensurate with its value within the range. I guess you could liken it to a modern Original 35 - another mass seller for Diana. It's still going well within the range and has a number of variants within it. It forms the basis of other models such as the 36 and 38 and nowadays is used as the basis of commemorative models such as the Diana 35 commemorative model celebrating the sale duration and numbers sold of that model by Diana. I can't recall the numbers I've got (under 5 I think) and they are a solid performer. I was particularly intrigued by the model improved upon by Sandwell field sports a short time ago.
In regards to the current Diana range there does seem to be some changes happening. A number of what I would have thought would be popular models have been dropped. I cannot recall the exact ones but the 52 is one that comes to mind. Also the Target Hunter range of guns that whilst eye wateringly expensive are excellent handling guns. Seems to me that Diana are consolidating their range to focus on those that sell well. I think they may have been a victim of their own extensive range of guns before now. Keeping them all going must have been quite a task with perhaps good sales of one model subsidising the poor sales of another. I can't think of any manufacturer that had such an extensive range of models at any one time.
Whether they have picked the right models to continue with remains to be seen. I think their Ntec gas ram range is very good. I'm not a huge fan of the new EMS model springer but I'm trying to keep an open mind. As for China- I sincerely hope not is all I can say (but I'll add that it seems that some low in the range starter and youth guns may be made there).
Cheers
Dave