Is the music used in openings made for the anime or it is an original song?

I noticed that in Bleach, there are some openings and endings music that are used before the release date of the song.

For example:
* Asterisk by Orange Range (Released in 23rd February 2005 but first used opening in 5th October 2004)
* D-tecnoLife by Uverworld (Released in 6th July 2005 but first used opening in 5th April 2005)
* Thank You by Home Made Kazoku (Released in 11th January 2005 but first used opening in 26th January 2005)
* (Non Anime Example) Sleepwalking by The Chain Gang of 1974 (Released in 26th September 2013 but used in GTA V trailer in 29th August 2013)

From these dates, I can think of two conclusion, either the artist made the songs for the anime or the artist use the anime to promote their songs. Which is the correct answer?