WARNING #1: this is a fast guide describing needed steps and providing needed files only for expert guys. It is *not*suitable* for newbies who need detailed instructions on how to install drivers, programs, flash partitions, etc...
WARNING #2: on this phone there are (strangely...) close ties between boot.img and recovery.img content. This involves that changing contents of recovery.img can produce bootloop and changing contents of boot.img can prevent to access recovery too, creating a soft brick condition. I don't know exactly why, BUT you are warned.
WARNING #3: the procedure and files provided are *only* for ROM1 firmware version 14 of 13 Aug 2016. It is indicated as OUKITEL_C4_V14.0_20160813 in "About phone" and as t637d-oq-s08-fdd3m-hd-64g8g-sd internally. If you are on a differently indicated version and/or release date, *don't*even*think* about trying to apply the provided files: bootloops and (at least) soft bricks are easy coming, expecially because of warning #2...
WARNING #4: all provided files are in .zip format only due to forum rules and limitations. They *all* need to be *unpacked* before use them.
CREDITS: this TWRP recovery has been compiled by Jemmini on 4PDA forum. Since of the Russian only language of that forum and the very hard way to subscribe on it for not Russians (needed to download files too...), I'm reporting it here with more explanations and my hints & experiences too...
Said that... Let's start!
IF (and *only* if...) your firmware version is reported as OUKITEL_C4_V14.0_20160813 in your phone, these are the steps to follow:
- unlock your bootloader (no special code needed, just enable the apposite option slider in Developers section of Settings and unlock it by the standard fastboot command in fastload mode... you need adb, fastboot and adb/fastboot drivers installed in your pc obviously )
Please remember that, as ever, unlocking your bootloader will factory reset your phone (and void your warranty...), so take it in proper account....
- using SP Flash Tool (recent versions since of the new MT6737 used in C4... tested one is the v.5.1644, just Google for it) just flash the provided twrp-c4.img (by Jemmini on 4PDA) selecting "Download only" on top, using the provided scatter file and selecting only the recovery row (browsing to twrp-c4.img file). Then press Download button and connect your phone in OFF status. If all was OK and you have MTK drivers properly installed (Google for them... search for MT6737 drivers. To test them just try to connect your phone to PC as storage to check if it is properly seen...), you should see a green checking sign "v" on top of SP Flash tool.
If nothing happens, try to reinstall drivers and/or doublecheck your phone is in OFF status when connected.
- don't try to boot to system now. It simply doesn't anyway.
For some unknown reason connected to warning #2, flashing twrp introduces a bootloop (soft brick...) on this phone.
Nothing to be worried of anyway: systemless rooting will fix it!
To root simply flash by TWRP (yes, you need to enable /system modification on first twrp boot...) SuperSU v.2.78 "standard" version in zip format (just Google for it...).
For standard is intended the released one, not SRx or "forced to system" one... (tested version is SuperSU-v2.78-201609011115.zip) .
Just remember that, since of unability to boot system before flashing SuperSU, its zip have to be already on your device before flashing TWRP. Otherwise you can use a microSD card to flash from it...
If you do all fine you now have your rooted & TWRP 3.0.2-x provided Oukitel C4!!!
If you are in a bootloop condition you aren't able to fix, just turn off your phone and, ever using SP Flash Tool in the same way, simply reflashing stock boot.img and recovery.img (both provided as zipped-to-to-be-unzipped attachment for... emergency reasons ).
After, if you want, you can install Xposed (in system mode) or busybox by app (it will be automatically installed in systemless mode since of supersu installation method...).
Don't even try to install Magisk v.9 instead: it will not work and will produce a soft brick (with no recovery access too...) that will requires a boot.img and recovery.img reflashing to be solved (with all this procedure to be redone one more time...).
This said... if you have questions... I'm here to answer them. Otherwise... have a nice time with your TWRP provided and systemless Rooted Oukitel C4!!!