Question [Q] samsung gt-i9502

Hello guys, i recently took from a friend a Samsung galaxy s4 duos, (gt-i9502), and as i informed, it was bought and delivered from chine, and it don't has even english language.. ( i don't know how, but my friend me that he add it the english language, and now it is displayed in English, but play store doesn't open.! With little research i found this guide: marrkdaviid(there are a dot, i can't post links)com/2013/08/fix-caller-id-install-google-play-on-the-galaxy-s4-i9502/ in which it refers to flash stock firmware and then flash with SVA_Rom v2.5, but in the second-third comment from a user, he is refering a way to flash stock firmware and SVA_Rom v4.5 which is something like 4.3, instead of v2.5 like 4.2.2.!!
When i try to follow the guide from the user comment i was unable to flash stock rom cause odin stops in cache.img and says FAIL!
The phone is already ( as i see from device details in 4.3, and baseband version I9502ZNUFML1) as i noticed the stock rom that the user prom to me to download is I9502ZNUEMK3, with MK3 in the end, firstly, what's the difference between the two, ML1, MK3, and secondly, and most important, can i proceed to flash the sva_rom with the current firmware (cause it gets fail to flash the other one..!! )????

PLEASE GUYS, I am new to forum, and i really need your knowledge.!!

regards from beautiful Greece.!!!