Part1. ACBL land
You are called to the table;
After South opens 1♦, West makes an insufficient 1♣ bid. (the software is too smart to allow me to make an insufficient bid in the diagram)
North tells me he will not accept the bid.
Reading Law 27B1(a) it appears that West can substitute the 1C with the lowest sufficient bid which specifies the same denomination, 2C, we don't address comparable calls until 27B1(b)
Do I stop here and allow 2C? , keeping 27D in mind?