If you tune in after the start of a live event, you will only be able to begin watching from the beginning on the B/R Live website or mobile apps. Presently, Amazon Fire, Apple TV, Roku, and Xbox One do not offer the ability to start from the beginning once an event has begun.
If you start the live stream two hours after the event's start time, you will not begin the stream from the start of the event so that the live stream won't be cut off once it concludes in real-time. If you join the live stream within that two-hour window, you would be able to start from the beginning of the event, but the stream may be cut off if your device gets refreshed. A replay will be available for you to view shortly after the conclusion of the event.