There seems to be multiple forms of HI used to cleave epoxides:
conc. HI, anhydrous HI, cold HI, hot HI, cold conc. HI, hot conc. HI, etc.
So, does concentration of HI and temperature have any significance in determining the product?
for unsymmetrical epoxides or oxiranes reaction takes place in this way:
in acidic medium- ring on reaction with HI ring opens from more hindered side i.e., the more hindered C-O bond. So the carbon in which more number of groups are attached which is bonded to the oxygen in ring gets -I.
in basic medium- the ring opens from less hindered side.
temperature is not a much important factor in this reaction.