Costlier versions of the Roadster, Model S, and Model X were available before the base versions were. If Tesla had done the opposite with the Model 3, that would have been the exception.
You're wrong about all of these: Tesla was clear that the more expensive Model 3's would ship first, and S and X both shipped the most expensive ones first.
Model X deposits ranged from $5k for the base model to $40k for the Signature model. Those deposits sat for up to 3 years for early reservations.
The upcoming Roadster requires $50k and $250k deposits.
The upcoming Semi requires a $20k deposit.
The original Roadster also required a deposit.
I'm unsure of the original Model S.
Tesla's current estimate for base Model 3's is "late 2018" for early reservation holders. Take that with a grain of salt given how reliably they announce unreliable release dates.
This is incorrect. As soon as you place your deposit, you're in the queue. The queue tool didn't exist until roughly Summer 2017, but deposits started March 2016. There was a period of more than a year where everything was opaque.
On another thread I asked if you have a source for this - I'll ask again, because I can't find one. I didn't follow the Model S/X stuff too closely leading up to the Model 3 (I don't spend that much money on a depreciating asset). I did put my Model 3 deposit down the first day possible, and I do not remember any such "clarity" you describe around timing and expectations.
Then again, originally my standard range Model 3 was estimated "Feb-Apr 2018" or something like that. It now just says "Late 2018" and I have no faith that will be met, either.
Source: sub-$70k model S buyer who had to wait longer than preferred for that to be available.