Damn, @Crawdad is absolutely right! I must have been totally blind (or deaf) when I listened to the single. Sorry bout that!
As you said, the 7" version of Breakdown is about a minute shorter (compared to the Rhenium version). It’s missing a part in the middle (about 27 seconds) and gets faded out earlier. I added both of them to Audacity and rearranged the 7", so you could see the missing part and where it fades out.
So yes, it appears we have three different edits of Breakdown. The single/HDH box version, the Rhenium version and the The First Thangs version.
The version of Red Hot Mama on Rhenium is however the same as on the 7". 