There are a couple things I feel I've taken for granted, and can't remember where exactly they came from, so I was wondering if anyone can remember if there's anything in game that supports this.

1. You can't summon the same primal twice.
If Ifrit has been summoned, and you try to summon Ifrit again, then the first Ifrit will simply receive all of the additional 'prayer/faith/belief' and grow in power instead.
This is the idea behind the Allagans sealing the Warring Triad alive to prevent the Meracydians from resummoning them, right?

2. For 'self primals', e.g. Shiva, Thordan, Tsukuyomi, and I guess Shinryu via Zenos, plus Ryne' Shiva too come to think of it... the Echo is instrumental in controling it.
Ysayle could control Shiva, Zenos via the Resonance could control Shinryu, but as for the rest, did they effectively temper themselves?
Which box does Ryne fall into?

Do I have this correct as per canon, or have I inferred sonething not explicitly stated in game?