1) You can unlock the bootloader again, each time will wipe your device however. I think you can use the same unlock code as issued by Motorola (provided nothing has changed with your device hardware - i.e. you have the same motherboard).
2)As I mentioned in the other thread, if you've hard bricked and you flashed the June 2017 stock ROM in its entirety - all commands and wipes, then you may be okay to accept and install OTA updates. This is dependent on you having flashed all parts of that stock ROM, so your device is at the same patch level - if you have not, then taking the OTA might hardbrick you again. The OTA updates do not necessarily include complete files, they mainly are a collection of patches, and assume your device is at the same patch level (GPT, bootloader, system, kernel, and other firmware are all at the June 2017 patch level, for example).
If you're worried at all about the OTA updates, wait for an updated fastboot stock ROM with the included update, which is safer.
3)Once you've taken any OTA updates newer than June 2017, it is no longer safe to attempt to flash the June 2017 stock ROM - if you want to go back to stock, wait for an updated stock ROM to be leaked. Else, you could downgrade (which I do not recommend), but do not accept OTA updates. Our newest blankflash works on B1:06 bootloaders, I do not know if it works on newer bootloaders. If not, and you hard brick, you'll likely have to wait for a new blankflash or pay for a new motherboard. A new motherboard is around 7000-10000 rupees or your regional equivalent, from what I've seen.