if i want to use old version, my phone will break.
I do not know the answer to that one because I never tried. Furthermore, with that question, you are off-limits on this discussion board. Here, I am not aware of any specialized enthusiast, who knows the answer to that one. The experiences from past software platforms like ‘Symbian/S60’ cannot be transferred to the current ‘Series 30+’ (MediaTek). Even with older platforms, whether downgrade works depend on several factors unknown to me. Sometimes it worked even directly with the Recovery Tool, sometimes you had to do more, sometimes you got a software brick.