Are the inlet valves made of the same material as exhaust valves or have different treatmnet?

Most intake valves are made of the same material as the exhaust. They are heat resistant treated high carbon steel, as are the valve seats.

The exhaust valve is usually larger in diameter to aid in scavenging of the spent hot exhaust gas.

Some more expensive engines have sodium (Na) filled exhaust valves to aid heat transfer

to the valve seat to help cool the valve.