is it safe to chase a gas cooker pipe into the wall?

Copper pipe can be chased through the wall. Must be taped and only use soldered fitting not compression. Cooker hose cannot be chased as it must be accessible.

Yes some will put a metal plate over the pipe for extra precaution but yeah totally safe

Must be buried at least 30mm into the wall, Have a yellow sheath around the gas pipe and have a 1mm metallic sheet in front of the gas pipe, But it’s always best practice to have it external in my opinion

"All gas pipework passing through a wall, whether or not it contains a cavity, shall pass through a sleeve. All sleeves shall be of a material that is resistant to corrosion, impermeable to gas and capable of protecting the pipework against failure caused by movement of the structure." Basically if your using 15mm copper gas pipe, you enclose this within 22mm copper gas pipe. This will protect against corrosion and structural movement.