How To Back Stock Firmware WRT1200AC

Hi My Friend,
Linksys Wrt1200ac first installed Openwrt Chaos Calmer 15.05 firmware. After that Chaos Calmer Web interface "Flash Firmware New Image section" Lede 17.01.2 open wrt I installed. After doing the process boot_Part 1 Chaos Calmer boot_part 2 Lede 17.01.02 Open WRT . After connecting rooter with SSH fw_setenv boot_part 1 When I make Chaos Calmer fw_setenv boot_part 2 Becomes Lede. How do I restore Stock Firmware in this case? I need your help in this matter. Thanks.

Yes, that line of devices have two sections; when you install a new OS, it goes into "the other" section, and from them on it boots into it. So, you always have the latest OS and the previous one. The original firmware is gone, and should be reinstalled as you would do on any other device. Have a look at the instructions at OpenWrt: