Interesting questions, all. How far back, and further and further back, might we humans ever be able to reliably go in our research before the unreliability is

Interesting questions, all. How far back, and further and further back, might we humans ever be able to reliably go in our research before the unreliability is too great? Will further computational advances, research methods and finds help? ... is there such thing as a "light (time) cone" beyond which we might not ever be able to look?