hi there is no diffrence between them, both of them are equal. In fact both of them are one word which means Party in English. میهمانی usually uses in written context and is more formal. مهمانی usually uses is speaking so ي after م removed. don`t worry this is not very unusuall, you can use both of them.

hello yes they are the same. no difference :) . maybe like "honto" and "hontoo" ;) better to use "مهمان"

こんにちはヤルダーさん 私はイラン人です よかったらあなたにペルシャ語を教えます میهمانیはمهمانیよりもっと丁寧です مهمانیはちょっとふうつけいです

salam "mihmani" and "mehmani" have similar meaning. but "mihmani" is more formal. مهماني とميهماني同じ意味です。でも、مهمانيは、懇談です。 がんばてください

just add it here that both "مهمانی" and "میهمانی" are most written formal.(it's better remove the ی from میهمانی ).and if you want to use as speaking formal then you'd better use مهمونی (mehmooni) which is more comon. Hope this help.