Okay why did you flash 920 rom when there is a sim free rom of the 925 no branding?
Sorry there has been a misunderstanding, Your first post "I tried to debrand my lumia 920 using nokia care suite but for some reason when I connected my phone it said that phone is not supported but in the readme it says it is? any ideas" said 920 so I assumed you were trying to debrand your 920 not 925!
I have flashed my new 925 Vodafone UK with unbranded UK 925 ROM. I only mentioned the 920 because I still have one and have flashed it with several different Roms in the past and here in the UK the unbranded roms for both the 920 and 925 do not support 4G (yet).
As for the question "I am interested in buying an unlocked lumia 925 vodafone 32GB but worried that flashing would lock the phone back to Vodafone again ? do you no if it locks the phone again "
With my 920 which came unlocked, I have flashed the EE rom and it did not lock the phone to EE and I have flashed it back and forth several times and the phone has never become sim locked!