DrMoze, why are you posting several threads on the same issue? https://www.mobileread.com/forums/showthread.php?t=16701
As I've said, send a private message in English here in THIS forum to the two people I have identified above. They speak English. Search this forum. I think porkupan has provided an English explanation of the process also in this forum. The process is almost the same as applying the hacks (using igorsk program) but instead of new xml files you are putting new fonts. Unfortunately, I do not have time to translate the instructions from Russian.
Yes, after the update, you will be able to read English, and Russian books. For my own reader I have also added support for Ukrainian and even Japanese (kanji and kana). As igorsk explained a while back on this forum, Sony Reader is Unicode-based. The only problem is that the three internal fonts do not include many Unicode ranges. By replacing the stock fonts with those that include desired Unicode ranges you will be able to read whatever language you want. Of course, the metrics of the fonts has to be similar to those of the stock font.