Since everyone seems to be on the same page, I think we can solve the shield.
Since Sy-Klone's getting all powered up, this thing acts as a little battery type thing and carries some sort of electromagnetic charge. So it's got a little extra punch to stun enemies, plus the magnetic property makes it return to him.
I'm deciding that the liberties I've taken with actual science are valid because Eternia's a different planet and there could be some magic involved.
For the chest, the Gars were allegedly total jerks. Sy-Klone is using the last one of these armors. When the Gar warriors were running around wreaking Havoc in their armors, there was some guy whose job it was to be the navigator, so he'd fly alongside the rest with a huge visible chest display, like a GPS for locating the ideal elemental conditions. The navigator wasn't much of a warrior, so he tossed his armor aside and got out of dodge when the fighting got fierce towards the end, and that's why his armor is the only set to survive.