Sounds like you are telling OpenRCT2 not to save its settings. It saves settings to your documents/OpenRCT2 folder by default. I suspect you have overriden the default save location and you don't have permission to write to the folder you have changed it to.
The pathing to the entrance does not lend itself to being a popular ride. You should always try get a junction at the entrance this will make more people use the ride. If there are more than one of this type of coaster that would also decrease popularity.
Develop does still have the occasional game corrupting bug that slips in every now and then. I would trust stable more if you are worried about corruption.
I don't think we save to a temp file and copy over. I'm pretty sure we just save ontop of the previous file. If it was too crash when saving it would wipe out the save. Although you say it crashed not when saving. I would at a guess have to say you might have just forgotten to save.
Some what. Most rides need different offsets and boundary sizes. And then the supports are obviously different for each track. There is a pattern to most of it so it's not hard to work out. You have to implement the whole of a rides functions before switching due to the way it gets called.
Its a bit easier but sadly junior rc doesn't have every track element type so its still a start from scratch for other types. marijnvdwerf created a very useful tool that tells you exactly what each track element needs to output which makes it much easier to make and check the other rides though. Recently IntelOrca has started doing a couple coasters so I think we will be ramping up over the next few months.
As for adding new elements in theory we could repurpose some of the existing elements that are not used for certain rides. It would be a bodge though that there would not be much reason in doing at this point in development. Wait for our own save format.
Sorry I was probably the one in the wrong to shoot down your suggestions so harshly. It's just this was the second long list of features I'd seen this week and the vast majority of suggestions are not possible for now.
So basically you think it would be super neat if we create a completely new game for the next update. Most of your requests are possible, some ridiculously difficult, some possible at the moment. The vast majority have such niche uses that there would be no reason adding so much code to implement them.
@sainty7 you night have to switch to a build from before the weekend if that doesn't work. I will revert my assert when I can but that won't be till tomorrow night