[Asus  Eee Pad Transformer Prime] UN Owen:
THIS IS A CLOSED CASE, GO HOME.

The answer is Hairybean found in step 2 of here [ROM] [TF201] KatKiss 5.1.1 - v30 [MultiWindow] [Stable] [RRO] Read the rest of this post if you're a sadist or want to know of people in the same pain boat as you.

Part 1: My life's story. Skip to Update if you just want to hear of my current problem.

So approximately 12 hours ago, I decided, "Hey, I want to upgrade my tablet so I can download the newest and coolest apps. Since I need to upgrade to a newer OS (ICS>KK ?) I may as well go through the extra hurdle and download a nice, fast custom ROM because the stock feels like crap for the lightweight that is the TF201."

Now me, not having ever touched an android in my life before this tablet, knew this was going to be a challenge. After doing plenty of research into unlocking, flashing a custom recovery, general custom ROM flashing etiquette, and following this guide ([ROM] [MM 6.0.1] KatshMallow v29 [TF201]), I encountered my first of many hurdles. This being: I was able to boot just fine, but the Wifi was in a perpetual state of "Wifi turning on..." I put a total of a couple or so hours into researching this and easily found others having the same issue, albeit not specifically to the exact ROM and device in question. I also tinkered a bit in these hours, reflashing and rebooting and all that jazz. I eventually settled upon one of three conclusions:

The "/persist" folder had gotten deleted which contains vital wifi/network configuration data

wlan0 was borked on a hardware level and I managed to completely kill an hope of wifi on my device

There was a MAC address somewhere that I needed to manually edit (that WASN'T in the persist file)

Considering the fact that I could not see nor change directory via adb terminal (yes, with su) into a "/persist" folder, and that the hardware-broken devices other users had were most if not all cellphones, I pushed on ahead assuming #1 to be my problem. ("See" includes dropping and installing a file explorer onto the tablet as well.)

With this is mind, the next course of action was to somehow get this "/persist" folder back. It seemed like the best way to do this would be to flash a stock ROM (link in Part 2) or ask the community to give me files without even trying to solve things on my own. So in the spirit of remaining a lurker I chose the former. Flashed fine, booted fine, ran.... okay-ish (the status bar "System UI" would crash every 10 seconds, ROM was a means to an end so I didn't care), but the Wifi WORKED! However, I still didn't find a /persist folder and the tablet didn't show up in windows... "Weird but okay, whatever let's do this." Load up recovery again, wipe everything, see if I can get Katshmallow to load again...

Part 1.5:

And here we are. tl;dr I'm a scrub at anything android and after 12+ hours of tom****ery, I'm in a bootloop using Katshmallow v29 (v27 made no difference). The "bootloop" is in the form of the ASUS logo appearing with the usual "UnLocked" message in the top for a minute or two, then a reset, rinse, repeat. I am able to boot into recovery and mess around in TWRP just fine, so my ignorance hasn't completely wrecked me... yet.

The information that I believe is most pertinent to my current issue is:

I unlocked using ASUS' utility for the TF700. It worked no problem and with how compatible things seem to be between the two, I don't think this is an issue (especially considering I've flashed and booted system more-or-less just fine).

The most recent ROM I flashed was this [ROM] TF201 JB JRO03C 10.4.2.15 (US) Stock Deodexed + Mods [Unlocked BL]. I figure that this did something (maybe changed the bootloader?) that Katshmallow does not agree with. If I hadn't already spent the better half of a day working on trying to get things working, maybe I would do more research and figure out the inner workings on my own, but I'm done bashing my head against a brick wall that's only pushing me further back.

I am currently running KANG TWRP 2.8.7.2 for the TF201T (yes, the device I'm specifically running). The problem existed with some TWRP 2.8.x for the TF300 as well.

The bootloader message is "Android card-hu-user bootloader <1.00e> released by "US_epad-10.4.2.15-20120917" A03 ... Oh son of a-

Part 2:

So I'm a dumb*** who can't read. Okay, I need to know how to get from my current bootloader (10.4.2.15) to the one Katshmallow requires (10.6.1.27.1). In typing this, I realized that the stock ROM I used to test stuff is why I've been screwed for the past 5 hours (coupled with my ignorance of course). In my quick 2 minutes of research I found this: [GUIDE][13/11]Update/Recovery/Root/Downgrade Android 4.2.1 on Unlocked/Locked Devices. I fancy methods 2 and 3, I can do those, but that doesn't change the fact that I know NOTHING about the bootloader and what I need to update it (but apparently I know how to give myself a headache by downgrading it).

Any help will be greatly appreciated. Oh, and if you know of how to solve the Wifi issue or the likely related /persist folder issue in the wall of text above, please I beseech you to tell me.

Disclaimer: My "research" is not at all limited to the links in the post. I've spent 90% (or more) of what's now probably 13-14 hours working on getting this piece of- getting things to just go right. So... tired...

Update: The problem has changed to my second post that I will be pasting here to save people the trouble:

So the problem as it stands now. I'm cannot seem to flash a different custom recovery and whenever I try to flash a ROM I get "E:Error executing updater binary in zip" The line above it, "symlink: some symlinks failed". I give up for now... Maybe I'll try again tonight. I'm running bootloader 10.4.2.15 and TWRP KANG 2.8.7.2 (which seems to require a 14.10 bootloader). In this mess, I don't know what to fix nor how to fix it. The angles I see are fix the custom recovery or fix the error/symlink problem since the bootloader version seems to be dependent on successfully flashing ROMs.

Update2:

So I managed to upgrade the bootloader by somewhat forcefully flashing Hairybean. While Katshmallow said "JB 4.2.1 BOOTLOADER VERSION 10.6.1.27.1," I glazed over this because I didn't know the importance of the bootloader and there was no other mention of the bootloader in the post (no mention of Hairybean or a download link or a "More information" link). I still have no one but myself to blame, just bitter that I have to blame myself in the first place.

For the time being, I'm following the somewhat better instruction on found in this thread([ROM] [TF201] KatKiss 5.1.1 - v30 [MultiWindow] [Stable] [RRO]) and will be picking up Katshmallow at the "wipe" step (currently waiting on the /data format). I downloaded the newest version of TWRP for TF201T and it's working just fine (note how that thread also doesn't mention anything aside from "MUST BE ON THE HAIRYBEAN BOOTLOADER ENDING IN 27.1" While that's such an obvious and blatant statement that should have inspired some research, my ignorance blinded me).

Now that I know for a fact that I am running the right TWRP and the right bootloader, I am going to pray that I can at VERY LEAST flash and boot into Katshmallow. Whether or not the Wifi problem persists will be for another thread.

IT BOOTS! YAAASSS. How do I close this embrassment of a thead?