Does every child of Wammy's House have a codename?
Yes, almost every child has a codename, all but Beyond Birthday. See next question for a complete overview of all characters related to Wammy's House.
The orphans use aliases rather than their real names, which are kept secret. In addition to these aliases, notable graduates may be assigned a letter by Watari.
Is the first letter from the codename the first from the real name?
Yes, the first letter from the codename is the first from the real name. Here is an overview of all characters related to Wammy's House.
The following list is formated as alias, letter, real name and relation. Also the following legend is used.
- (-) Indicates that the character does not have a Letter.
(†) Indicates that the character is now deceased.
Watari, W, Quillish Wammy, A famous inventor and philanthropist, founder of the orphanage and assistant and mentor to L. (†)
- L, L, L Lawliet, The famous detective L. He was found by Wammy as a child and brought to the orphanage. The goal of the orphanage is to train a worthy successor to his title.(†)
- Near, N, Nate River, The youngest of the two boys in line to succeed L. He takes on the mantle of 'L' by the end of the series.
- Mello, M, Mihael Keehl, The eldest of the two boys in line to be L's successor. He leaves the orphanage soon after learning of L's death, and gives the title of 'L' to Near. (†)
- Matt, (-), Mail Jeevas, He is the third smartest student at Wammys, though not a successor to L. (†)
- Beyond Birthday, B, Beyond Birthday, The second child of the "first generation" in line to succeed L. He eventually ran away from the orphanage and became a serial killer. (†)
- A, A, Unknown, The first child of the "first generation" that was in line to succeed L. All that is known is that he committed suicide. (†)
- Linda, (-), Unknown, A female student who appears once, when she asks Near to come outside to play. She is referred to later as being a successful artist.
- Roger Ruvie, (-), Roger Ruvie, A close friend of Watari's who runs the orphanage in Watari's absence.
X, Y, and Z - Only briefly alluded to at the end of Another Note, they are referred to by Mello as three children that appeared in the "Detective Wars" bio-terror case with L.
Various other children are depicted in both chapter 59 and the one-shot special's flashback, though none are given any names.
- K - A former student of Wammy's in L: Change the WorLd, who has become part of a bioterrorist organization which plans to "cleanse" the world of its excess population by a deadly virus.
- F - A former Wammy's student and colleague of L's that dies early on in L: Change The WorLd, while on a deadly rescue mission in Thailand.
- D, P, Q, G, I, E - Shown on L's mailing list in L: Change the WorLd.
- R, V, T - Also shown on L's mailing list however their letters are grayed-out along with B's, implying they were killed.
- J - A character in the D.S. game L: The Prologue to Death Note. Due to the game not being available in English, little is known about him, but based on his name, it is assumed that he is from Wammy's.
Source Death Note wiki
PS: I wanted to put the list in a table as on the wiki, but the formatting seemed to be completely off. Anyone know of a way to format tables on SE?