No worries, but in my case I'll try to be brief if You don't mind ;)

The plasma as 4th state of matter was not really an association to blood, was me messing around ;P

Separating Cells

All I can say in a simple way is that the same way oil and water, sand and water, etc.., don't mix, the cells too have different compositions, densities, masses, and memory ( probably stored in the water.. ) to not mix up things when not needed, otherwise we would be a blob!

Yes that analogy is correct to a degree, they are transported to where they're needed and transformed through a chemical reaction, electrical and maybe magnetically ( frequencies?!.. ), to fulfil the needed function.

Water Memory

I don't watch movies ( used too but.. too much propaganda, and much more to do.. )
I do believe neurons act as ROM and water as RAM =P

Breathing Water

Let me answer this with a question:
What do You get if You separate Oxygen from water?

Hydrogen gas (dihydrogen or molecular hydrogen,[13] also called diprotium[14] when consisting specifically of a pair of protium atoms) is highly flammable:

2 H2(g) + O2(g) → 2 H2O(l) + 572 kJ (286 kJ/mol)[note 2]

The enthalpy of combustion is −286 kJ/mol:[15]

Hydrogen gas forms explosive mixtures with air in concentrations from 4–74%[16] and with chlorine at 5–95%. The explosive reactions may be triggered by spark, heat, or sunlight. The hydrogen autoignition temperature, the temperature of spontaneous ignition in air, is 500 °C (932 °F).[17]

I used to like a lot of those shows.. Not important now, still, will say it has a lot to do with mind control..

Nano Tech

I don't trust either distrust any tech, all have their potentiality of being put to a constructive/productive function =)

GMO's I don't really think are a good thing, in my opinion, anything that goes against the nature of anything else is a "no, no!!"

That is good, I used to build computers, now, mostly repair what I already have when in need to.. ( ..miss that old times.. )

Spraying Nano Tech

Geoengineering is every freakin'where!! On this one, for as much as I would like to disagree, not possible! It might as well get to that point, where we might need to self engineer the body to the point of injecting nano-tech, BioAPI, to fight back..

Yeah, nano-technology is being studied for quite a while now, those are just known patents from 2018, we can't even imagine what is closed behind doors, to be registered in 20 Years, after a ton of predictive programming propagation for it's acceptance..
( I think DataAsylum has an entire page dedicated to cures/possible cures.. )

Seven Years

I do too sympathize with number seven, so much I have one painted over the door of my room ;P

But, I don't believe the 7 Year theory right away, I just allow it to be considered as a very probable one, until proof I believe nothing!!
( Not really but You get what I'm saying, I think ;).. )

And even in the even of cancer cells loss, maybe they were not needed in the first place, so I don't care about "replacing" them, much less forcing anything to the body, let nature do it's thing, just rest enough, eat properly, do some exercise, meditate and pray and everything should be fine ^^,

Cell replacement doesn't exactly work as You're describing, plus we are constantly expelling dead cells, new ones being made to replace them in most cases.. The lvl analogy You used is actually wrong, we can produce top notch cells even better than the previous ones, given that we provide resources for the body to create a better environment for the respective cells.. I think our cells are always at 100%, again, given the appropriate environment ;)

Now brain is a whole different story..

We still have people living quite a long time, with diets based in rice and sweet potato exclusively, having a majority of centenaries and with life expectancy averages way higher and much healthier..

Still there might have been people living more than 200 or 300 Years, might..

Creating Blood

I'll try to put it in this way, if You have thermal paste, and don't want it to eventually solidify becoming waste and actually clogging/preventing heat dissipation, You keep it in its container, protected from air ( Oxygen ), whenever ready to use You put it between two plaques lets say processor and cooler where it will be in contact with air, and heat that will do most of the damage, and in the same way our cells, nervous, blood, pretty much any of the 11 main ones, or around 200 different ones depending on the complexity of the function of the respective organ or tissue. Any of them will react with Oxygen, by norm oxidizing, so I guess You see why the body contains most things separate of the majority of water, to avoid contact with Oxygen =x.. Even thou most of our body being made of water..

Plasma

Here we go..

Plasma is created through Transcapillary filtration on the capillary walls, if I'm not mistaken, in the liver..

For now it's more than enough x)

( ..brief I said x_Ð.. )

Take good care ;),
Cy