The Fairytale ending is the result of deciding to marry the Prince. To do this, simply declare the intent to do so when given a choice. (Choose Go For The Prince)
Linked below are four separate foolproof guides that will gain you all of the variants of this ending. It would be near impossible to list every possible combination of the variants, so I have simplified it to four simple guides that will unlock each variant in the Ending Viewer section of the Rewards menu. This way once you have unlocked them all, you can view each ending and mix and match variants via the viewer.
If you wish to play through the game with a different combination of variants than listed in one of the four guides linked below, you will need to follow and combine the directions/choices listed under "Variants" for how to unlock each specific variant. For example, if you wish to play through the game to gain the ending with the Fair Queen, Loves Tobias, and Independent variants, you will need to make choices listed under "pro good" and "pro smart", spend time with Tobias/flirt with him, and avoid befriending any of the advisors. By combining variant requirements like this, you can mix and match endings. Be advised, however, I do not think a playthrough of every combination of variants is possible, because many choices made throughout the game are contradictory. If you want a foolproof method to gaining each of the variants, use the guides linked below.
Refer to this page for personality variants choices (aka "good"/"bad"/"smart", "pro tobias", "pro carmosa", etc.).
Linked below are the guides to unlock every variant of the Fairytale Ending:
Type of Queen
1. Fair Queen: Be kind as well as intelligent. (Be "pro good" and "pro smart". To do this, balance the points between the two categories.)
2. Evil Queen: Be selfish and lazy. (Be "pro bad")
3. Machiavellic Queen: Be intelligent and manipulative of other people. (Be "pro smart")
4. Good Queen: Be kindhearted and naive. (Be "pro good")
1. Tobias: Spend time with him, flirt with him when given the opportunity, and if he likes Cinders well enough he will ask her for a date. Afterwards choose to kiss him or ask to go to his house for the night. He will accept if Cinders was bold enough in her pursuit of him, or refuse if she wasn't bold enough. (Be "pro tobias")
2. Perrault: Meet with him at every opportunity and openly flirt with him. When he invites Cinders to the lake, choose "How about me?", she will then make her move. (Be "pro captain")
3. Prince: Be intelligent and Cinders must have no other love interest. (Be either a "Machiavellic Queen" or a "Fair Queen" and be "pro prince")
4. No Love: Fail to make Tobias, Perrault, or the Prince fall in love with Cinders.
1. Fairy Advisor: Be on good terms with the Fairy. Tell Ghede you believe in magic, visit the lake and leave a gift when instructed to do so, and accept her help when offered. (Be "pro fairy")
2. Carmosa Advisor: Be in Carmosa's good graces and admire her skill when Ghede remarks on it. Obey her without question, don't be late, save her 25 sovereigns, and befriend Gloria and/or Sophia. (be "pro carmosa", and be either "pro gloria" or "pro sophia" or both.)
3. Ghede Advisor: Befriend Ghede. Agree with her that people are stupid, that Carmosa is exceptional, and tell her that you have your ways when she asks Cinders what her plans are. (be "pro voodoo")
4. Independent: Fail to gain the Fairy, Carmosa, or Ghede as an advisor.