No, the original Sony A7S requires an external recorder connected via HDMI to capture 4K video. It records up to 1080p Full HD internally.
Yes, it is legendary for low light. With a maximum expanded ISO of 409,600 and large individual pixels, it produces usable images in near-total darkness.
It uses the Sony NP-FW50 rechargeable Li-ion battery, providing approximately 320 to 380 still shots per charge.
The Sony A7S features dust and moisture resistance, but it is not fully waterproof and should be protected during heavy rain.