No problem about the questions. Although the answers can be found in the forum, from time to time, maybe a recap of the story/situation is needed… 
I’m sure others will add more, if I’ve forgotten something:
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As you see in the shop there are two identical phones, each with different price. The more expensive one is assembled in USA, if you value that. Both should be equally scrutinized and secure, but I suppose it depends on potential customers feelings which they prefer (which they trust more… or less… etc.). Conversations about it: Librem 5 USA edition
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I’m not sure about what you are assuming here, but it is a phone and most parts are integrated, so mostly they are not upgradable. That being said, the battery is changeable and it’s possible that in the future there could be a better one available. The radios (wifi, cellphone) are changeable too (with a bit of effort) and there has been talk that you could use a bit different combinations (radios better suited for different parts of the globe, different networks), but that’s not really an upgrade - more like an optional feature. Unfortunately memory or processor can not be upgraded (more space with a memory card though).
Edit to add (related to radios): In the official FAQ, it says: Will the phone support 5G networks? Librem 5 will have M.2 slot for a baseband module, so it is a potenital for “upgrade”. But when we first start shipping Librem 5 this probably won’t happen, as 5G is relatively new and still in testing.
Then again, if you were referring to the batches (Aspen, Birch, Chestnut, Dogwood, Evergreen… and Fir), “A” through “D” can be thought of as development stages (“betas” or “release candidates”, if software terms can be applied) which some have opted to get, despite knowing that there will be unresolved issues. Evergreen is supposed to be the final version of Librem 5, sold to the public (the “normal” and “assembled in USA” variations - I’m unsure where the “A” through “D” were assembled). So, no, you do not have to buy all of them - in fact you can only get the “E” now (unless second hand).
The Fir batch is a different thing and for clarity, in my mind, shouldn’t be named a batch, as it’s a different version and probably an upgraded design compared to L5 (as it has different processor and probably other updated design choices). Best thought of as a possible new future model. That one you’d have to buy separately as there is no upgrading to it from L5. But at this point, there is no certainty about if and when it’s coming.
On a related note, upgrading should not be as necessary with L5 as with most phones as it uses Linux (and has that replaceable battery). Software updates should continue wayyyy into the future. Some discussions about that: How long is the lifetime of Librem 5? and Librem 5 Longevity: Solving The Problem of Disposable Technology
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Originally this was a crowdfunded project, so payments were made - can’t even remember anymore how long it’s been… - back in 2017. It was supposed to be finished 2019 (spring, then fall - and then the batches were announced, so technically Aspen meant it was shipped). At that time they started to sell it to everyone else too, but original backers are still first in line as most of us are still waiting for Evergreen. Which should arrive in August the earliest. That was the estimate a few months ago and since Dogwood is only now supposed to be shipping (next week, hopefully), a few months late, it’s likely that August is a bit optimistic (there is probably a need to do stuff after “D” version testing and feedback). Six months seems like a rough estimate, considering the delays and the queue of other customers/backers.
There is likely (who knows) enough bought already, so Purism does not need to wait for more. More likely, when it does finally come out, there’s going to plenty of new customers lining up to wait, extending that estimate. But at the moment, as L5 is essentially “a first”, a prototype of it’s class of phones, from that perspective it’s understandable that estimates about development time to finalized product and shipping are more “guesstimates”.