Optimize (install of JIT v2) (plugin for 2.1 phones only from 2010 line).This can make your phone stuck at the SE Logo) Clean your rom (remove /system/apps of your choice) (Be careful, unless you really know what you do, do not modify the default list.Install recovery, busybox, custom kernels.This said many rooting scenarios are available implying kernel only downgrade to retrieve a patched rooting exploit and then flashback the right kernel. Using the flash tool, you can choose what to flash and what not to flash.Using official sony tools, you can only upgrade.Once bootloader unlocked, official sony tools do not work anymore.But flashing firmware is still the core of Flashtool (that is updated at least to follow Sony improvements around sin files) and the reason for its name. From time to time, sin files have been bundled into what is now well-known FTF (Flash Tool Firmwares) and more features have been implemented. We worked together to add more features to the tool such as rooting methods implementation or TA backup/restore Then I took the lead and got some advice and help from him occasionally on some features like rom cleaner or bootloader unlocking. Based on a command-line tool written by Bin4ry (Andreas Makris), I brought a user interface to sin files flashing. This program was originally made to flash sin files downloaded by SEUS or PCC.