The question is: can this acid be substituted in any way, shape or form in any of the formulas which require sulfuric acid?
It depends. One thing you need to be aware of is that AgSO4 is quite water soluble while AgCl is not. So if you for example look at the dichromate bleach in b&w reversal processing, HCl would not work instead of H2SO4. If you pH adjust a C41/E6 bleach which already contains plenty of Br-, Hcl should work as well as H2SO4.
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