For each sentence,
Specifically, each sentence can be deciphered as follows:
Unless dermal standards myelate solely willingly, energy tangentially gullies into uric membranes, orbitally, eventually.
Iodine cannisters, notwithstanding, bear twosomes live within outer units.
Theremin arsenals reverberate sunsets to connect tin units.
I think I got the basic idea, but either I am missing something, or the message is not quite in RP English.
It seems that you get the other sentences by
These are the results after some pretty liberal interpretations, hopefully I didn’t get too inventive:
My prefix is a big ol' ass,
My infix always comes before;
My suffix straight up lies bruv',
About the answer that I bore,
I told ya who I am already, know what I mean?
Clues are hidden in both the title and the rhyme, once you find the answer everything will make sense, Good Luck.
Found after rainfall, in all continent,
Can be found also in sinful ...
Partial answer for part 3:
The text in the image is
Solving for X and Z, we get
and then, something along the lines of
Part 2 looks like
Part 1 seems to be a list of
but I've yet no idea what to do with it. For starters,
Although my 日本語 is a bit rusty,
So one of your favourite poets is
Taking each three-number code $m.n.p$ to mean
another of your favourite poets is
Another of your favourite poets is
Thanks @Deusovi for help with this!
Thanks to @OmegaKrypton for all but the suffix here.