降级 用英语怎么说？

downgrade the system

「降级」在手机数码中指 downgrade the system，把手机系统回退到旧版本。

After the update my phone became laggy and the battery drained fast, so I decided to downgrade the system.

更新后我的手机变得卡顿且耗电快，所以我决定降级系统。

You can't downgrade the system without unlocking the bootloader, and doing so may void your warranty.

不解锁引导程序就无法降级系统，而且这样做可能会失去保修。