Gas lines must be tested and passed, prior to being put into service. Around my area, the new work is first isolated.... meaning.....it's not connected to the natural gas lines that already exist. One end of the new work is capped off and a guage/fill valve is put on the other end. Compressed air is used to bring the pressure inside the new work to a specific value. There are two tests. One is a "one hour" test and the other is a "24 hour test". The pressure inside the new work cannot drop less than X number of PSI during these periods. If the gas fitter is satisfied that his work meets this criteria, he fills out a tag that identifies him along with other required information and that tag is wired to the work he did. I cannot say to a certainty as to how this is done where you reside. In my part of the world, plumbing inspectors pass plumbing but they don't pass gas fitting. That work is inspected by the local gas utility because it's their product that is going through those pipes and if there is a leak, it's their a$$ that gets sued. Therefore, if I was in your shoes, I would be calling the company that supplies gas to you and insisting that one of their service techs come out and make sure that everything has been done to code and is 100% safe. Most likely it has but isn't that phone call worth the peace of mind that comes with it? After all, if you knew what you were doing, you wouldn't be asking questions on this forum, now would you? Gas is nothing to be trifled with. Three or four days ago, a complete home was blown apart due to a natural gas leak. All that was left was a pile of smoldering rubble. They are still looking for the remans of the woman that was inside at the time. See the link below. The gauge assembly likely belongs to that poor SOB who got screwed by the GC. You are lucky that he did not put a mechanic's lien on your property. Technically, you owe him for the work he performed. You obviously had an agreement between yourself and the first GC as to the total cost of putting this addition on. If you got this addition completed for less than that amount, then why not locate the gas fitter, pay him and give him back his guage? Imagine for a moment if you were the plumber/fitter? You had to pay your supplier for all that material plus eat the time you put into the project, all because you trusted someone. When talking about legalities, there is always a moral issue that goes hand in hand with it. Here is a link that might be useful: explosion

Removing the flex line and capping the valve is the correct way to cap the line. Also, flare fittings do not require any pipe dope. Just make sure the cap is tight.

I'd continue talking to the folks at the Gas Co. myself. What would happen if one of the workers hit the gas line? What would the company do in an emergency situation? We had a worker hit a line when we were working on a home in the East Bay area and it was a scary situation, but PGE responded quickly and turned it off via a line in the street. One would think they could kill the feed long enough to install a valve somewhere along the line without tearing up everything. Then, when the construction is finished they'd use as much as possible of the existing line and add new where needed. Sometimes you have to call the gas company several times to find someone willing to work out the problem! As sierra said, the line up to the meter can only be worked on by the gas company.

Julien sinks are handmade. They have specialized sizes and a wide variety of options. Their 16 g sink is very thick and the finish is excellent. It's a beautiful sink and top of the line as far as stainless is concerned. Franke is another high quality sink with excellent configurations. I've not seen a Kraus sink in person nor have I owned one. I did buy an 18 g Elkay drop in for the laundry room and it's nowhere near as nice as the Julien. Having owned both, I would only buy an 16 g for sound and durability. There is a difference in the grade of stainless used in Julien sinks and the Chinese made brands but I'm not sure it's enough of a difference to matter to most people. If a top of the line sink is a must, or their sizing is needed (I needed a 30 x 16x 10-inch sink which is difficult to find) then Julien is the way to go. Their accessories are expensive but, if the sink is installed for it, they have a cutting board that can slide across and a steel strainer as well. I really loved the depth of the sink as my kitchen space was limited and it gave me huge flexibility for prepping and reduced splashing. I'm tall but with the grid I didn't find it too deep at all. Otherwise, Kraus 16 g is a great value and there are many styles. It's an opportunity to save some money with 0 difference in function or looks.