A transportable tank designed with ASME Sec VIII Div 1 and meeting IMO/ IMDG regulations.
Design pressure/ MAWP = 1.77barg,
Test pressure = 2.65 barg
Relief valve set pressure = 2.2 barg.

This relief set pressure is not meeting ASME Sec VIII requirements however vendor says it meets IMDG requirements (I have no idea about IMDG requirements) and approved by class companies.

my question here is whether IMO/ IMDG regulations superseeds ASME Sec VIII Div 1 requirements?

I have seen many of these tank containers.
I'am 99,9 % sure that this vessel is not U-stamped.
IMDG requirements do not supersede ASME requirements. For Div. 2 there is the code case 2624 which permits the DOT setting for pressure relief devices.