At what level of completion is it usually released?
The answer to that question is basically "when it's ready".
The dev has planned for a total of 4 releases including the already available version for the game to be completed (check the devnotes in the OP) but there is no planned timeline for the releases because the dev works on the game in his free time so it will take as long as it needs to between each update.
Also the game is free for everyone (no patreon or subscribestar paywall) so no one can complain if it takes some time, we just have to be patient.
If you want to speculate on how far along update 2 is, I'll give you some numbers.
The total so far for all progress reports combined for update 2 is:
- 98 renders
- 26 animations
- 1.5k words
And the numbers for update 1 (current version) are:
- 364 renders
- 23 animations
- ~14.5k words
So if update 2 is about the same size as update 1 then the progress on renders and animations is quite far along but the scripting is only 10% done.
But as I said, this is just speculation, update 2 could be bigger than update 1.
And here is the most recent progress report from the dev that was posted yesterday.