How to pipe a propane kitchen correctly

Just purchased a new house and found a great surprise, a 500-gallon propane tank buried in the backyard. Not sure how old it is, but it is holding gas, a gas contractor came out and checked and it still has gas. The previous owner was using it for the pool heater, but they switched to electrical, now it is unused.

We want to install a gas cooktop, we are remodeling our kitchen and our GC and the same gas contractor said that we should run a line from the cooktop to the outside of the house and said we could use copper. So my GC installed this 1/2 inch type L flexible copper from the cooktop area to the wall outside, (in the floor) wrapped it in a 1" electrical PVC pipe so it has long 90" elbows, and installed new tile on top.

We called a plumber this morning and he came out and said that we should have used a rigid pipe, and that he will not go near the flexible pipe. He also suggested that instead of running a line from the existing tank, to just had a new 100 gallon tank and place it near the kitchen wall and use a flare connector to hook it up.

Any recommendations on what I should do here?

Do i need redo the floor? Please say nooo