I'd like to root, install custom recovery (preferably dual) and back up the phones original state including TA partition, then move on to updating to a 4.4 Kitkat build, probably stock as I will leave the bootloader locked for the moment.
Despite having worked on (rooted etc.) 2x Xperia SPs, I have read through the many Z1 rooting threads and ultimate guides and I have no idea where to start. Most rooting threads start with downgrading, which I shouldn't need to do, there are usually multiple methods for each firmware version and most don't seem to root the currently installed ROM (especially the newer firmware versions), they require a ftf file (of unknown SI number) flashed over the current ROM. There doesn't seem to be a way to retain a firmware version with the correct SI number for my phone.
I think I read that Bin4ry's rooting method is the best for this firmware. Is that right? The dual recovery seems as though it could be problematic, will it be overwritten when I update or flash an ftf file? Once I root the original .518 firmware etc. what do I do next to get to rooted Kitkat (.757)? Is it possible to get a rooted 4.4 stock ROM with the same SI number? Should I actually be bother with such details?
I could really use some clear advice on the best way to proceed.