The gas pipe runs from where it is connected to the outside of the house - runs above the basement ceiling - across 3 rooms to the various connections on the other side of the basement. Approximately ~40 ft.

Luckily the ceiling is open in the room where it enters the house & also open where it connects to all its distribution points. But the ceiling is closed in between in the 2nd room (gym).

My father's recount of the plumbers' estimates is that it appears the leak is closer to where the gas entry is & therefore over a non-closed ceiling.

My questions are:

1) The gas company won't take responsibility for any gas issues within the house - is this true?

2) If the leak is indeed over an unclosed ceiling - can the pipe be replaced without tearing down the middle room's ceiling?

3) One plumber is charging $1600 but requires permitting & no replacement of ceiling.
Another is quoting $2100 with no permits & no ceiling cutting. Appropriate for the work or reasonable?

4) Is this where insurance is worth a call?

Would appreciate the community's feedback on this please.

TIA!

You won the lines after the meter.

"2) If the leak is indeed over an unclosed ceiling - can the pipe be replaced without tearing down the middle room's ceiling?"

Depends on details not present here.

"3) One plumber is charging $1600 but requires permitting & no replacement of ceiling.
Another is quoting $2100 with no permits & no ceiling cutting. Appropriate for the work or reasonable?"

Call your AHJ.
Some places may consider it enough of a repair to not require a permit, many others will not.

"4) Is this where insurance is worth a call?

Insurance does not usually cover maintenance.

You folks here are real life savers!