I probably won't implement getting it early. The point is to be kind of like a puzzle and figure out the steps to get the item before the ceremony and a reason to actually attend the gathering before it begins, so the reward is to witness the Light in the evening.
Can you explain further? Saves carry over when you update the game. On Windows, the save data is located in C:/Users/<user>/AppData/LocalLow/Whitecrocus/The Spirits of Sabil
Have rope in your inventory, then if you keep mating with Ori or Sean, they will eventually ask if you want to use your rope to do bondage during mating. Then you should get the achievement.
During the Light Ceremony, ask Sean about how to protect yourself from the Light and he'll tell you get a spirit stone and you provide it to the Spirit Tree to get Spirit Protect. There is a hint that Ori will tell you to ask Sean if you ask Ori or went to the ceremony with him/her.
To complete that achievement, call the moki cute when they first appear in the Summer so they return the second time. In the second visit, call the moki "more than cute" and give the right responses to mate with the moki, then you should get the achievement.
Only unlockable as male MC. Chat with Ori while he/she is mateable and bf/gf and Ori will ask to go swimming as a date. After the event, you unlock the BJ scene.