That was a simultaneous release with 'If I Were A Boy', not the same thing at all as being an earlier B-side.

it was only urban radio single in US and wasn't released as single in global market originally. it was B-side in global market.

it got single treatment later in few market after became viral hit.

I think Elvis' 'Hound Dog' was originally pencilled in as a B-Side (to 'Don't Be Cruel') but then both took off

 

This 60s instrumental 'Green Onions' is an iconic piece that a lot of people would probably recognise but not necessarily be able to name:

 

 

charted at #3 in the U.S. and belatedly at #7 in the U.K. (after usage in the film Quadrophenia) - while I think the original A-Side 'Behave Yourself' made no noise

Another one is David Bowie 'Suffragette City' - originally a B side to 'Life on Mars' in 1972 but released as an A side in 1976 to promote a Greatest Hits. Failed to chart though.

Everything She Wants by Wham which was the B Side to Last Christmas temporaily became the A Side after Christmas 1984 was over.

Cold Heart by Paula Abdul was B side to Straight Up in the uk.

And I think Opposites Attract was B side in the USA

Wasn’t Bohemian Rapsody a B Side??

 

The first time in 1975 it definitely wasn't. The second time in 1991 they were planning to release Those Were The Days Of Our Lives in time for Xmas, and I think when Freddie died in November they added Bohemian Rhapsody to the single as a tribute to him, but I think it was then always promoted as a double-A rather.

The last number 1 of the 1950s, What Do You Want To Make Those Eyes At Me For by Emile Ford and the Checkmates, was a b-side - the a side was called Don't Tell Me Your Troubles.

1963 by New Order was the B side to True Faith in 1987. A remixed version got to number 21 in 1995.

"Just a Day" by Feeder was originally the b-side for "Seven Days In The Sun" at the start of 2001, and was then released as a single in its own right at the end up the year, and ended up outpeaking the latter (#14 vs #12).

Shatter was also the b-side to Tumble & Fall, before being a AA side release becoming one of their highest charting hits (#11)