Individual States can deviate from ICAO standards. I don’t know the procedure involved, but the nature of the difference is published in a supplement to the relevant ICAO Annex, e.g.
Annex 6 Part 1.
The question about not descending below MDA on VNAV has been discussed before – try search.
Some states have considered (may be allowing) a small descent below MDA which has been justified by a risk/safety assessment. Note that there are differences in obstacle/terrain clearance between ICAO PANS-OPS and TERPS.
IIRC, TERPS has a lower clearance and hence a descent below MDA would involve greater risk.
Microburst2002 re NPA table – please make it an Altitude / Distance table – reasons
here. Emphasis on checking altitude first.