cipher - The Twenty Doors (ROOM 10)

This is part of The Twenty Doors series.
The previous one is The Twenty Doors (ROOM 9)

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There is some paper taped to the door in Room 10:

Well done! You are now halfway! To mark this event, this cipher is EXTRA hard!

- ???

You then look at the main paper

PART ONE

To decrypt the first cipher, I've given you a mathematical equation:
$d(x) = a-1(x - b) \mod\ m$
a is 11, b is 25, and d is the decrypted text.

Izea ahx lprp z cjrqg hjay mx rdrp, kla ja pazeap hjay nexmp.

mmking solves it without dying, so you get to Part 2:

PART TWO

Everyone loves a mime. MDEwMDEwMDAwMTAwMDAxMDEwMTAwMDAxMDAwMTExMDAxMDE= The other key is key. Wmb wmmuh, drh imqfo tdvw ubonbv lcfkmod rr d vdqirp vrzugb isu bbd jbqbvdwmsr, fqh nv kmvwxfooc xrgudgbdgoc. Jr wr qc kbgwnwb, kmwmx pc rdpb. Wmbub, csx empo imqi wlb frwkbv.

PART TWO - HINT ONE

'My name' refers to something recent in The Twenty Doors series, but not this part. Go back through each one, see if you can find something useful...

As requested, here is the contents of the site page.

My name again. J2I. Pga torooapr fpi Rlis Mcrcl ym otmplx tv Gsic 10. Iepzve aud hb, cap pbqi hb dnui ub. Befud. I hate vowles, exept for i.

PART THREE

CodeNewbie is still working on getting at the password, but here is the ciphertext:

Irrt sthcgma

Also, like magic, a keyboard appears, with the letters A to Z on it!

PART 3 - HINT 1

! Spinny! @HHF G L\NFHP301 3@WDXECT R1T0||0T GTFDHPSRX5R 3ARHCU/ £A NT S0! If you can be bothered to decode that, you've then got to work out my L3etspeak. :) It's Markdown O'clock!

PART 3 - HINT 2

L3etspeak is usually written with two three's (L33tspeak). So, what could that three mean???

There are going to be three separate parts to Room 10, thus it is a semi-interactive puzzle. The next part will be added when this door is solved!

Answer

The OP added the following sentence in this comment:

Here's a hint, because I'm getting bored of waiting:
ahhltomot eiXect fcu eutnsr ee lnfhqso SPUN THREE TIMES!

This is a 3 column transposition cipher. After some manual adjustment, this decodes to:
Search the left column of the question

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Part 3, Hints 1&2 - This is also a 3 column transposition cipher. After some manual adjustment and translation from Leetspeak, this decodes to:
Search the far right left column of the page to find the password

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Part 3 - Based on the hints: "all up, not down", "left column", "(markdown) format read", "except for lines that are >Quoted or >!Spoilers", "eleven characters (not a word)", and "forget the stars", the password is:

pTCPAPmYTTT

Final Answer - By subtracting this password from the ciphertext (irrt sthcgma), the final answer is:

type seventh