Getting Started
Starting the challenge is simple. I would recommend beginning a new game.
Founder Creation Rules
Your founder's name must start with the letter "a".
Your founder must be a Young Adult or an Adult (though Young Adult is my personal recommendation, to make it a little easier).
After you've created your founder, pick a house for them to live in! The freerealestate cheat is allowed, but I'd advise you to not go overboard with your founder's house.
Gameplay Rules
Death and Reloading Rules
No reloading a previous save after Bad Luck, but you may restart a previous save, if you so desire, after a Catastrophe. What's the distinction? Bad Luck would be something like a baby being born a boy when you wanted a girl or a fire starting. A Catastrophe would be something like an accidental death or a child being taken away by CPS.
A death by Cow Plant, if automatous, is classified as a Catastrophe. A death by the Mother Plant, however, is classified as Bad Luck.
Additionally, bringing Sims back from the dead is allowed, if said Sim is directly related to the Sim bringing them back. However, the Sim who gets brought back is not allowed to marry and have children.
Reloading a previous save to fix a bug or a glitch is allowed.
Cheats Rules
No money cheats.
No immortality cheats (ex. MCCC's Flag For No Age).
MC Command Center Rules
I'm including this as a section because of the amount of people who use MC Command Center. If you don't use this mod, these rules obviously do not apply.
Automatous WooHoo must be set to False OR Risky WooHoo (the value that decides whether or not normal WooHoo results in pregnancy) must be set to 0.
Automatous Proposal must be set to False.
Fill Household Needs is allowed, but only if it's really bad. For example, if the toddlers keep trying to go to bed, can't somehow, and are keeping everyone awake, you can use this cheat. Just try to keep its use to a minimum.
It's recommended to set the Marriage and Pregnancy checks to "Bypass All Played Households", but not required.
General Gameplay Rules
In the Settings menu, make sure the Auto-Aging setting is set to "Active Household Only".
Have Lifespan set to "Normal".
The Legacy Family
This is where this challenge differs from other Legacy challenges.
The founder's children's names must start with the next letter of the alphabet. Example: "My founder's name is Amy and her children are Beth, Carlos, and Dawn."
Each of the founder's children must have the same number of children as the founder. For example, if the founder had three children, each of those children must have three each. As such, keep your founder's amount of children small, unless you want a chaotic family tree and an extra challenge, not to mention the risk of culling.
The rule above has one exception--if any Sim has an unexpected multiple birth, then the others do not need to have another baby. The extra baby's name can either begin with the same letter as the planned baby's name (Example: "Dawn had surprise twins. Her children are Elliot, Freya, Gabriel and Grace."), or can begin with the next letter (Example: "Dawn had surprise twins. Her children are Elliot, Freya, Gabriel, and Hannah.").
Spouses are allowed to bring money into the family.
All children can be moved out of their home lots, provided that they are Young Adults or older.
Use of a Trait Randomizer is completely optional.
The Legacy Family must have a Family Cemetery. The Family Cemetery must be a large lot, to accommodate all of the tombstones that will be accumulated. The cemetery must have a barrier around its outer edge, either a fence or hedge, but otherwise can look like whatever you want it to be.
Additionally, one Sim in the family must be the "genealogist". Being the genealogist means that they must be present whenever a family member dies to collect the family member's urn/tombstone and put it in the Family Cemetery.
Succession
There are two version of succession in this challenge.
Version 1: No succession.
This version means you play rotationally between each of the families you have. It can swiftly get chaotic, so it's not for the faint of heart.
Version 2: The youngest child is the heir.
This version is less chaotic. This version means that whichever child was born last will be the next played. In the event of a plural birth, whichever child was named last will be the heir. Example: "Dawn's youngest child is Grace, so Grace is the third generation's heir. After Grace's youngest child becomes a Young Adult, they will be the fourth generation's heir."
There is no scoring system for this challenge. As such, the only way to lose is if you give up the challenge. If you make it to Z, you win!