The firmware downloaded from openwrt is openwrt-18.06.2-brcm63xx-smp-R1000H-squashfs-cfe.bin
Login V1000H through web browser, go to utility and upgrade firmwire, choose the above .bin file. But failed as "not support format" error. Seems it looking for .img file which not supplied in openwrt.
I don't know the device in question, but what makes you believe that "Actiontec R1000H" and "Actiontec V1000H" are the same?
Both devices seem to exist, and at least judging from the case design they look similar, but that doesn't mean its internals are necessarily identical (even small software differences, like partitioning, h/w ID, GPIO assignments necessitate a dedicated image, which might be easier to create than starting from scratch, but it still needs doing).
Aside from that, the missing device page and incomplete techdata/ wikidevi pages don't really tell much about the device (R1000H), but at least the commit adding support for the R1000H suggests BCM432x WLAN, which would imply that it's only barely supported by b43 (no 802.11n/ HT support, 54 MBit/s at most, not very stable for these chipsets); if you want to use its WLAN capabilities, OpenWrt is probably not a good choice for this hardware. Furthermore the ADSL/ VDSL (or cable/ HPNA) hardware isn't supported at all.
Well, the thread you mentioned doesn't say that it was successful.
If you still intend to try, be advised that you may very well end up bricking your router, and if it works then you are likely to have certain functions not working, as @slh pointed out.
If I were you, I'd save the device and the effort, and swap the router for a one that I know is supported (unless you don't need it).
A bit late, but I did manage to get openwrt working on this. It seems like the V1000H is the same as the R1000H except for the RJ11 for xDSL. The R1000H firmware would probably work except the V1000H has an extra signature check. Once the openwrt image is flashed CFE doesn't seem to care about the special signature and you can flash it from the boot loader. For the first install though, the procedure is: