RShara

Brandon's not ready to make it canon, but is leaning toward them snapping back to their full age, similar to atium.
 

Well, Hoid is an Allomancer. But I don't think he was really drinking cologne. I think he had a different disguise just before that, and the cologne is a remnant. And he passed off the discrepancy as claiming he was drinking it.

The strength of the Copper burner is also a factor. So they'd need a lot to pierce The Lord Ruler's coppercloud. Not quite as much to pierce Elend's. A coppercloud doesn't affect yourself, iirc, so TLR wouldn't need to pierce his own coppercloud.

Oh that scene. Later on in chapter 15, it says
So to me, it's clear that he was placed there by either those ropes or different ones, earlier.

Shardplate is considered a type of god-metal, so it's inherently invested. Although whether it's the remnant of a spren is still up for debate.

They should be written correctly in their Coppermind articles if you want to look them up.
Investiture, each of the Realms, Connection, Identity, Fortune, Shard. Intent when used canonically is capitalized. When used non-canonically in reference to the name of the Shard is lowercase.

It's still Ruin and Preservation. They're intermingled but still disparate, like homogenized milk, or dirt and water making mud. They could be separated out but it would be difficult and take effort.

Yep, it would negate the magical cutting effects of a Shardblade, but it's still a very soft metal against a hard, sharp, pointy object.
FYI, you can find the collection of answers that we've gotten from Brandon (called WoBs or Words of Brandon) over on wob.coppermind.net, aka Arcanum. The search is pretty easy. This one comes up under "aluminum+shardblade" for instance, and is a great resource for questions that have been answered

I think they all technically get access to both surges right away. The only real exception to this that we've seen is the Skybreakers, and I believe that's because of how strictly structured they are. Like, Szeth could use Division right away (he was a Squire first, we don't see any limitations on Squires), but he's told not to because that's not how they train their recruits.
Kaladin: Definitely used Gravitation and Adhesion from the beginning.
Shallan: Definitely used Transformation and Illumination since the beginning.
Lift: Definitely used Progression and Abrasion from the beginning.
Jasnah: Hard to say whether her initial encounter with Ivory involved Transportation or Transformation, and we don't really see her progress, so we don't have enough evidence there.
Renarin: Definitely used Progression since the beginning. If his visions are his version of Illumination, then he's used that since the beginning too (The countdown that started early in WoR).

There's a slow drop off for each type of magic.  It's really noticeable for Elantrians because they get that huge Elantris boost.  If they were to go to Fjorden, Aons would function at about the same level of power as the Monks' does in Arelon. 
The Monks have also figured a way to give themselves a bit more power while away.  Seems to involve human sacrifice, if I remember the books correctly.
 
 
 

This one?  https://docs.google.com/spreadsheets/d/1JJtJhHwpKdow01n2-bsT3scVvqJd6lZh4uvpNwcslv8/edit#gid=0

Mistwraiths breed true, so I think there would still be mistwraiths.  Sazed wouldn't have eradicated the species, imo.  But they're kind of myths currently.  I don't think any of the current cast has seen a mistwraith other than the kandra.
Unfortunately, I don't think it's possible for a human to be turned into a kandra without the intervention of a Shard.  Their biology is just too different from a normal human's.

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Wow, what a doozy of a first question.  The answer is.......really complicated, because each one would affect the others differently, and we don't have a lot of information on that interaction.
We know that hemalurgy can be used to steal power from any magic system.
We know that stormlight can be used to fuel Returned so that they don't need to live off of peoples' Breaths.
We know that stormlight is an easy investiture to convert to use in other systems.
We know that allomancy (Mistborn) would be really hard to get working with another system.
Brandon has described using one magic system to power another as "hacks." 
Each person wanting to use another magic system than they normally could would need to hack the system to get it to work.  We've seen Vasher hack it so that he can use stormlight instead of Breath.  He hasn't, however, figured out how to use stormlight for Awakening.
 
Here is a good collection of Words of Brandon or WoBs about hacking investiture.  https://wob.coppermind.net/adv_search/?query=hack
 
Beyond those, we're not really sure how hacking investiture can or does work, just that it can usually be done.  Sorry for the less-than-complete answer!

Can you link to the Coppermind article?  It sounds like there might be some confusion in it.  Brandon's addressed this question.