1. last_kmsg required ROOT permissions to access it.I enabled local terminal from Dev options but opening the terminal made the device restart. Then I installed Termux but it said- no such directory found after writing the command (su -c "cat /proc/last_kmsg" > /sdcard/last_kmsg.txt).
Today the device started restarting itself in a loop. It became unusable to I had to flash the ROM again. Then I installed TikTok Lite v17.9.1 and opening it trhice or twice made the phone take restart. I tried to grab last_kmsg via SysLog App (last_kmsg option is greyed out) and Termux (Operation not permitted) but none of those worked.
Note that now the ROM seems quite snappy & smooth after reflashing. But random freezing and restarting issues tend to appear after a few days of usage.
2. You have to pull them at the first boot right after the reboot.