Ok, let's start. I'll do this in order.
The Uti Possidetis borders made by Spain. Chile claims(or claimed, since it renounced its claim to the Patagonia to avoid Argentina from joining Bolivia and Perú during the War of the Pacific(1879-1883)) that the Patagonia belonged to the General Captaincy of Chile, since Bolivar ratified the Uti Possidetis after the Independence(which was made worse when Alto Perú became Bolivia, causing confusion with every country neighboring Bolivia.) of South America. But Argentina claims that the Patagonia, as well as Southern Chile(from the Mapuche and then south.) belonged to the Viceroyalty of La Plata.
The two sides claim both sides of the Andes.
During the early days of the 80s the Carretera Austral(Austral Road) finished its early construction(after starting in 1977), getting more and more extended as the years passed but isn't finished yet. That's for the Chilean side.
Argentina started its road in 1983. So, not even started in 1978 or 1982.
So, bad for both sides.
Unexistent in that region. Railroad reached only Puerto Montt in Chile. Over 1,500 km away from Punta Arenas. Same in Argentina. It didn't reach that far. Transport was almost exclusively by air.
Mines, the few that existed there were unvaluable(when compared to the North(of both countries) or completely empty for 100 years.
No, they prefered to be left alone. Chile made German/Italian/Croatian inmigrants take the land of the Mapuche(who also live in Argentina) since the 1860s. Argentina slaughtered the Onas/Selk'Nam starting in the 1880s. From a small population of 4,000~5,000 people, in 20 years it was barely over 800. The other tribes(like the Chonos, or the Kawesqar, or the Yagans or the Tehuelches) were extinct since before the Independence,(or just not seen since then) at the brink of extinction, all pure members of the tribe dead, and extinct in Chile and barely alive in Argentina, respectively.
The southern tribes are basically just a list of genocide committed by Chile and Argentina.