No. LG V30 Plus does not have the notification light since it has the Always-On display.
LG V30 Plus is IP68 certified. It means it is water and dust resistant. It is also 810G US military certified product.
Yes, LG V30 Plus does have the face unlocking support.
Yes, LG V30 Plus can record 4K videos very easily as the rear camera has the highest video recording resolution of 3840 x 2160 pixels. You can also record 4K videos with Hi-Fi audio recording.