The game has a wiki, so you can find a more detailed explanation there.
TLDR: heritage points have to be spent to do anything, They are refilled each run, so there's no point 'saving' heritage points for later. Instead you simply try to increase your maximum between runs.
As for when to prestige, unless you're stuck and want a fresh start, it's generally a good idea to wait until you've built a wonder, since those persist until ascension. So the typical game loop is:
- play until you've built a new wonder
- if you want, prestige immediately, or you can play a while longer to try and conquer the world map, get more heritage exp, royal points etc.
- if you didn't prestige after building a wonder, you prestige when you feel stuck and not making progress
- just before prestiging, try increase your population, even beyond what you can feed/sustain, and you could demolish other buildings to make room for more housing, just to get more prestige exp from population
- repeat until you have all the wonders, then you can try doing a 'conquer the whole world' run if you want, or ascend for more RP
If your first run gives you 2 HP, it means on your next run you can spend 2 HP, leaving you with '0 out of 2 HP'. When you abdicate in your second run, and start your third run, you will again have 2 HP to spend (unless you earn more, then you will start with more), that's what 'refilled' means. You always start a run with full HP, and abdicating can increase your maximum, so you'll start with more. It's not possible for the maximum to decrease (except if you do a hard reset).
HP can be spent to buy more land, or to buy technology without having to research it. Both only affect the current run. So you could see this as 'getting your HP back when you finish a run, so you can spend it again in your next run'.
It seems mostly finished. It looks like the author got it to a point where it can be considered a 'finished game', and moved on.
I guess officially it is a version 1.3.10, and probably version 1.0 is what the author considered to be the 'full game', with updates 1.1, 1.2, and 1.3 adding some extra content, reworking some existing features etc., and some other minor updates being mostly bugfixes and such. But as you can see there hasn't been much going on for a few years, so I wouldn't expect new content at this point.
As for the wiki, well... it's a small game with a very tiny playerbase. Probably some player at some point created the wiki, the author probably linked it in the game because it was the best documentation for the game available, even if incomplete... but then probably the original wiki author lost interest. In the end, wikis are meant to be a community effort, where anyone can fill in missing information. For big games with a big community it works, there's always people willing to update the wiki. For a tiny game like this, not so much.