Path of Exile Dev Tracker

The "take x fire damage" will occur (potentially igniting you) before the removal of ignite. In this case both are caused by the same thing, so this is effectively arbitrary, but it's that way because internally stuff that is explicitly only for a specific ailment (Eye) happens before stuff that's general for any ailment (shared suffering removing) due to the way the code is structured.

Eye's "take fire damage" is part of the "apply an ignite" process, where shared suffering removing ailments is part of the "apply all the ailments this hit will apply" process, which is a step "further out" - so it occurs after all the individual ailment functions have been called.

Yes, if the damage taken from RF (and any other degen) is more than or equal to 20% of your max mana per second (which is very likely).

If RF is somehow dealing less damage than 20% of mana per second, then the mana drain will only be enough to exactly counter degen.

However, this doesn't and can't account for other forms of life recovery that are also countering RF - it can't "see" any other forms of life recovery, just total life loss per second, so it scales it's effect to counter that, even if you have enough regen to already fully counter the damage.

1) No. First the damage of the hit is calculated. You aren't shocked yet, so that modifier isn't in effect. Then the calculated damage is applied to the enemy - this shocks the enemy, and because of the reflection, the same shock application also applies to you. Once shock application is done, shared suffering sees that you applied a shock, and thus removes shock from you.

2) I'm not clear on specifically what you're asking here, could you please clarify in more detail what interaction you're asking about?