The seven Divine names?
The following are the Divine names that may never be erased: Yud Kei Vav Kei; Adniy; Keil; Eloka; Elokim; Elokaiy; Shakaiy; Tzeva–os; Eh-yeh.] It is forbidden to mention any of the designated names of G-d in a bathroom. This refers to the seven names which may not be erased.
May one recite the letters of the name Havayah or must he say Yud Kei Vav Kei?
One is not to recite even the letters of the name and is rather to say Yud Kei Vav Kei.
May one say the name Tzeva-os?
Yes. However in Eretz Yisrael some are accustomed to say Tzevakos. According to all one is to write Tzeva-os with a dash.
May one say the name Eh-yeh?
One may do so if he does not intend to say Hashem’s name and is hence saying it for other reasons.
 The list of names is found in the Gemara Shavuos 35a; Rambam Hilchos Yisodei Hatorah 6/2; Michaber 276/9. There are various versions and discrepancies between the Rambam and Shulchan Aruch as will be explained in footnotes below.
 So writes Rambam Hilchos Yisodei Hatorah 6/2; not included in the list in Michaber 276/9; However see Kesef Mishneh ibid that brings another version of the Rambam which does not include Elokaiy, and so concludes Gr”a ibid to be the correct version.
 These are the seven names listed in Rambam Hilchos Yisodei Hatorah 6/2; See Kesef Mishneh that explains why the Rambam did not list the name Eh-yeh, and why the Rambam lists eight names if in truth they are seven. One explanation is that Adniy and Yud Kei are one name. Another explanation is that the true version of this Halacha in the Rambam omits the name Elokaiy.
 Michaber ibid; Not listed in Rambam ibid, see Kesef Mishneh ibid
 85/3; Michaber 85/2
 See Nagid Mitzvah in name of Arizal; Radbaz 5/1; Chasam Sofer Choshen Mishpat 192; Eretz Tzevi
 See Sheivet Halevy 9/217; Kinyan Torah 3/110; Mishneh Halachos 13/198; Rebbe in Hisvadyos 1983 2/850 that so is the custom.
 The reason for this is because the name is also used for mundane purposes to refer to the legions of an army. [Rebbe ibid] or because the name is never used alone in the Torah and is always adjacent to another name. [Kinyan Torah ibid] See also Halichos Shlomo 22 footnote 32; Piskeiy Teshuvos 215/12
 See Halichos Shlomo 22 footnote 10; Piskeiy Teshuvos 215/12