This full tutorial applies to the Galaxy S2 I9100, I9100m, I9100t, and I9100p (no NFC)
DO NOT ATTEMPT ON ANY OTHER VARIANT
The method is similar for the i777, i727, and T989
But the ROM, recovery, and partition files are different
Any Android 6.0, 6.0.1, 7.0, 7.1, 7.1.1 /
Cyanogenmod (LineageOS) 13, 13.1, 14, 14.1 ROM
can be flashed using this method
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FILES TO DOWNLOAD:
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Odin 307:
https://drive.google.com/open?id=0B-ZEipHEvWB6d3lVNDRkd1FfNHc
CWM recovery:
https://drive.google.com/open?id=0B-ZEipHEvWB6YnlmejFubWVOU1U
Marshmallow Kernel:
https://drive.google.com/open?id=0B-ZEipHEvWB6bmxJb01HZWxWQ1U
IsoRec TWRP:
https://drive.google.com/open?id=0B-ZEipHEvWB6TEtxc081MVNMNW8
Re-partition flash-able file:
https://drive.google.com/open?id=0B-ZEipHEvWB6MDB4ZEVxUDBCelE
Alternate name pit file for anyone having trouble:
https://drive.google.com/file/d/0B-ZEipHEvWB6TjNLeDNwMTVFMHM/view?usp=sharing
Resurrection Remix:
https://forum.xda-developers.com/galaxy-s2/development-derivatives/rom-resurrection-remix-t3507366
OpenGapps:
https://opengapps.org
use ARM 7.1 and whichever version you prefer (I have only tested nano)