first 2 bytes of slot setup are current kernel/rootfs, next 2 bytes are newest. during startup device always try to boot using newest. it’s not important for you, because even if you set them 00 00 01 01 they will change to 01 01 01 01 after reboot.
firmware 1.4.7 comes with update of ble app from version 123 to 125, but i don’t think you will run into any problems using new version with old kernel/rootfs. if you do, you can always downgrade it via telnet.