Part 3: When you happen to delete BRAY(tmp=2, life=2), you cause BRAYs to die prematurely, thus advancing the BRAY lifecycle under your cursor by a single frame. The wall of BRAY loses its integrity and BRAYs with different life values (and shades) appear.
Part 2: The ARAYs shoot BRAYs at the existing BRAY(tmp=2, life=2)s, thus creating BRAY(tmp=2, life=1). This BRAY(tmp=2, life=1) dies before the ARAYs could shoot another BRAY over it from the right. That's due to evaluation order, but that's a complex topic and I wouldn't get into it in a comment section. After that, the ARAYs once again create BRAY(tmp=2, life=2). This is behind the fast blinking effect.
Part 1: It's because PSCN-sparked ARAY generates BRAY(tmp=2, life=2), which, of course, has 2 frames left until it dies. That's what happens when this BRAY is created over air, but when it's created over other BRAYs, it's created with life=1, that is, it has one less frame left to live and is also darker.