Is double-faced cashmere warmer than a normal lined blazer?

It is warm for its weight because both faces are cashmere, but it is not a winter coat. It suits mild weather and indoor layering better than deep cold.

Cashmere pills, and double-faced knits are prone to it at cuffs, underarms and where a bag strap rubs. A cashmere comb removes the pills, but expect some fuzzing with regular wear.

How should I clean it?

Dry clean only. Do not machine wash or tumble dry, and brush it and air it between wears to stretch the time between cleans.

What is the difference between the high collar and shawl collar versions?

The high collar sits closer to the neck for a more formal line. The shawl collar is softer and more cardigan-like, better for casual layering.

Does it have a lining or inside pockets?

No lining. The double-faced construction is joined by hand, so the inside shows the reverse of the cashmere and there are no conventional inside pockets.