Okay, so:
1. It's been mentioned here before, but Rogue-Like: Evolution is a big one. I think the sex scenes system in that game is great for a sandbox format and I realized it could work really well with randomly generated characters, too. Other than that, I liked the sandbox approach in Degrees of Lewdity and how you have this world map with all these different areas to do.
The fantasy setting is really just a combination of different tropes that I thought worked well for an H-game.
2. Yes, it's my first game, which is why I'm learning a lot of things on the go. I do have some basic programming experience and I did make a short visual novel with Ren'py for my friends before, but other this is the first time I'm working on a big project like this.
3. - The way I envisioned it, I want the world map to be split into regions where you will be able to go and then either do some dungeon crawling or encounter events like a bandit ambush or a friendly merchant caravan. There will also be capital cities of foreign nations that you will be able to visit to engage in diplomacy.
- I want the game to be a sandbox through and through, so I probably won't be doing proper game over endings, but I do have some end-game goals in mind that will have a lasting impact on the game. Those would mainly be: completing the main story and finding the Fountain, finding a spouse/spouses and get a co-ruler in the form of a Queen/King, and finally, interacting with foreign nations.
All this said, I want the kingdom to be dynamic. How you rule will actively change Evalia, so if, for example, you rule with an iron fist, people on the street will fear you, whereas if you're good and popular, everyone on the streets will be going crazy over you. The factions will also play an important role in that if you're a sympathizer of, let's say, the Church, the kingdom might become some form of theocracy of union of State and Church, and if you frequently work and support criminals, Evalia will turn into a lawless city, attracting more pirates, smugglers, and theives. The shifts in goverment will also be influences by the Order, Fame, and Depravity meters, so that if you become a theocracy, it might take on a more dictatorial form with high order and low fame, something like a cult, or with high depravity and high fame, the city will become one large sect that organizes orgies on the street and evangelizes their beliefs all over the world.