Also I'd Thank @abhayruparel for helping me flash this GSI
1) First Of all Your Internal Storage Will be wiped out so backup important data
2) U need to be in Non Treble TWRP Download Link
3) Then Decrypt First by formatting data partition (Go to Wipe ---- Format Data)
Note ecryption is an important step do not skip it!!
4) Reboot to recovery
5) Change Data partition to f2fs
Note :- If at any point TWRP gives error message like failed to format or mount /data , reboot to recovery
6) Change data partition to ext4
7) Wipe System, Data, Internal Storage, Cache, Dalvik Cache
8) Now reboot to recovery even if u are on recovery
9) Now Flash Treble TWRP by mike Download Link
10) Reboot to recovery again (Mandatory)
11) Now flash los 15.1 Official only no other zip Download Link
Please do not boot into the ROM because it automatically encrypts and all your previous efforts will be in vain!!!
12) Now wipe System, data, cache, internal Storage
13) Now Flash Android P semi GSI in system (Remember the GSI file which you will download will be ".zip" file , extract it from PC and use the ".img file") GSI Link = Download Link
14) Reboot to twrp again This is mandatory
15 Now go to mount and check all the Checkboxes, mounting vendor is mandatory
16) Then Flash Post Zip 1 = Download Link
17) Then Flash Post Zip 2 = Download Link
18) Then Flash Post Zip 3 = Download Link
19) Then Flash Incall fix zip is not needed in Developer Preview 4 !!
20) Then Flash p lag fix zip Download Link
21) Treble Magisk = Download Link
Now Reboot to rom and viola U will have android P gsi boot on ur P2!!!
Bugs that i found While Using this GSI (Kuntao Specific)
Camera mode switching takes 3 to 4 seconds to open
Sometimes it lags for 3 to 4 seconds (not a big deal tho)
Double Tap To Wake
I have found these much bugs so far if you find any more Please report it!!
Now a video tutorial for this is live on my channel !!!! Youtube Link
Note = All the links that i have shared are not my works all the zips are made by @erfanoabdi .
Also Official Treble Los 15.1 and Treble TWRP is made by @mikeioannina , i am just sharing this. as a guide For download link of the GSI and additional Information please visit this thread