On October 17, 2002, Selena's family was interviewed by Julie Chen of The Early Show about Ones. Chen asked Selena's father and manager, Abraham Quintanilla, Jr., about his intention to re-release Selena's songs on Ones. Quintanilla told Chen that because of the success of the 1997 biopic about Selena's life, many new fans know who she was. Chris Pérez (her widower) told Chen that Ones was released for Selena's new fans in the wake of the 1997 movie, explaining that the family used the DVD to showcase Selena for those who never saw her perform live.
The recording was released as part of the Selena: 20 Years of Music collection, a nine-CD retrospective of Selena's musical career. The other eight CDs were re-releases of her studio albums: Selena (1989), Ven Conmigo (1990), Entre a Mi Mundo (1992), Amor Prohibido (1994), Dreaming of You (1995) and the compilation albums Mis Primero Exitos (1990), Live! (1993) and Live! The Last Concert (2001).Ones was released on October 1, 2002 by EMI Latin, and included audio statements by her family, friends and members of Selena y Los Dinos. On November 11, 2002, Unos was released in Spanish-speaking countries with the same track listing as the American edition.
The first of Selena's number ones on the album was "Buenos Amigos", a duet with Salvadoran singer Álvaro Torres which helped her tour in Torres' country and throughout Latin America. "Baila Esta Cumbia" and "No Quiero Saber" were from 1990's Ven Conmigo; the latter track peaked at number six on the US BillboardHot Latin Tracks chart. "Como La Flor" (Selena's signature song) and "La Carcacha" were both originally on 1992's Entre a Mi Mundo. "Como La Flor" launched her on the Latin music scene, according to critics. The song was acclaimed, and was credited as Selena's first number-one single (despite Billboard's official record of the single peaking at number six). "No Debes Jugar" (the lead single from 1993's Live!) and "La Llamada" made the album cut. Sally Jacobs of the Boston Globe called the recording one of "her cumbia signature songs" and "most popular cumbia song[s]". Four of the six number ones on the album were singles from Selena's last studio album, Amor Prohibido (1994). The title track sold 400,000 copies in the United States and was number one on the Hot Latin Tracks chart for nine consecutive weeks, one week short of the record for most weeks at number one on the Hot Latin Songs chart. "Bidi Bidi Bom Bom", the second single off of Amor Prohibido, spent five consecutive weeks at the top of the Hot Latin Tracks chart. The third single from Amor Prohibido to be featured on the album, "No Me Queda Mas", peaked at number one for seven weeks. Following Selena's death in 1995, the song spent another eleven weeks in the top ten (twenty-six weeks overall on the Hot Latin Tracks chart).
"Si Una Vez" peaked at number four on the Regional Mexican Songs chart, while "El Chico del Apartamento 512" failed to chart. Her posthumous number-one single "Fotos y Recuerdos" spent seven consecutive weeks atop the Hot Latin Tracks chart. "Techno Cumbia" peaked at number four on Billboard's Latin charts. "Donde Quiera Que Estes", a duet with the Barrio Boyzz, is Selena's second number-one duet. "I Could Fall in Love" and "Dreaming of You" are the only English-language tracks on Ones, and are her most recognizable recordings to American music fans. Both tracks were taken from her crossover attempt, Dreaming of You (1995), which was released posthumously. The only other track from that album, "Tú Sólo Tú", also appears on Ones (Selena's sixth number-one single on the album). "Siempre Hace Frio" was originally released on Siempre Selena (1996), her first remix album. A.B. Quintanilla III and Pete Astudillo composed "Con Tanto Amor Medley", a medleymash-up of "Amor Prohibido", "Si Una Vez" and "Como La Flor". The track was produced by Kike Santander and Jose Luis Arroyae. Tatiana Morales of CBS called it a "beautiful ballad", but John Lannert had the impression that the medley was composed to "fit [in] various Latin radio formats." He noted that the recording had a pop twist with acoustic guitar and "discreet strings", calling it "tasteful bolero-like percussion". Because of the mariachitrumpets used in the "Como La Flor" part of the medley, Lannert thought the track was aimed at regional Mexican radio stations. He was disappointed by the dissolution of the "saucy cumbia beats" that "originally took these songs to the top of the charts", but called "Con Tanto Amor Medley" "[a] rare medley that achieves a seamless transition from track to track" and "manages to sound cohesive, generic arrangements notwithstanding". Lannert ended his review by calling the track "an appropriate balance for an homage."
Ones reentered the Top Latin Albums chart the week of February 7, 2004 at number 74 before slipping off and reentering the chart the week of March 13 at number 65. It placed number 62 the week of April 1, reaching sales of 400,000 copies. After 77 weeks of release, Ones was in 70th position on the Top Latin Albums chart the week of April 10, 2004. The following week (April 17) it rose to number 11, achieving "greatest gainer" status from its previous position.Ones slipped off the chart the week of May 29 from number 66. The 14th anniversary of Selena's death sparked a 51-percent increase in sales for Ones, which rose to number four on the Top Latin Albums chart (up 61 percent from its previous position). In February 2010 the RIAA certified the album gold, signifying shipments of 500,000 copies in the United States.