obviusly says that the frimware its only compatible with 720n(CN) v3 and v4 soo my question is could i brick the modem if i try installing the frimware ? or it gonna work normali?
According to the wiki page, your device does only have 2 mb flash and 16 mb ram... This is not sufficient to run openwrt/lede.
Also 4 mb flash and 32 mb ram isn't that much fun with openwrt/lede.