Q1
I am not really sure how your answer explained why the Picts could not be subjugated by the Romans.
Q2
Hadrian’s Wall was started sometime around 117AD and completed around 128AD. It was in use until the fall of the Empire in 410AD. It had its peaks and troughs of use during this period whether behind the lines or as the northern defensive line. It also got over-run at times.

Thanks for your input.