Not always. It only works with FIP/MIP connections. If it's a compression fitting you're just wasting money.

Compression fittings first question is "can you use a shark bite push fit instead?"

Second thing is, get a small amount of food safe grease and put it on the copper ferrule to make the connection: took me far too long to learn that.

Definitely. I'm more worried about the valve in the pedal being faulty and leaking.