If people with hiv could take a 750mg difflucan at single dose, could normal people or animals (not affected by hiv) take it too, or there is certain properties that hiv patients have so they could ?

Such an extremely high dose of fluconazole is only used for serious fungal infections; if taken by someone with HIV, probably that person was diagnosed with a serious opportunistic infection because of his or her immune deficiency. There is rarely a need for anyone else to take such a dose and for sure you should not do so if not so advised by your doctor.