Znalazłem na stronce ovi.h1n.ru taki tekst, przytoczę go (po angielsku, tłumacz się kłania):
Outlook on firmware downgrades with BEST
Several tutorials illustrate the opportunity to downgrade Symbian^3 devices with BEST, including this very demonstrating video on YouTube. Nonetheless, you should be aware of some unpleasant or questionable features that BEST has, what makes the entire downgrade process highly risky or not applicable at all. According to the mentioned instruction, after all backups were created and before starting the downgrade flashing, the additional required step is a complete flash erasure. To do that, go to the "Repair" tab, check "Rapido Safe" box, and press the red "ERASE FLASH" button. Without disconnecting the smartphone from cable, reinsert the battery and press the smartphone's power button for a second (until the log appears). Then accept all queries and wait for the process to complete. Yet, some things need to be carefully considered. Most significantly, this step is utterly destructive in terms of flashing with BEST. If you disregard all warnings stated here and now, and wish to proceed anyway, your phone will be bricked de facto! The only concern is to what extent it will get damaged. For instance, if you do the complete flash erasure on first-generation Symbian^3 devices (Nokia N8, C7, and similar), you will not be able to flash anything else except for stock Symbian^3 and Symbian Anna afterwards. It is because everything will be wiped, including CMLA. And BEST cannot restore CMLA, although various kinds of backup were created, including FullFlash. Symbian Belle will not boot with damaged or missing CMLA, and the only known way to restore it is by the ATF programmer. On the other hand, second-generation Symbian^3 smartphones (Nokia 603, 700, 701, and 808) tolerate damaged or deleted CMLA, and the erasure step does not affect a normal boot. But, there may be potential problems with the regular DRM, which is quite necessary for correct device operation. For example, unlike various CFWs, stock Belle FP1 / FP2 always contain EMMC file which is packed with several pre-installed games. During firmware flashing, DRM keys are imported into a phone's memory, and they are essential for launching the games involved. It is a matter of opinion whether or not DRM keys will work with damaged CMLA. As a result, you might never be able to flash OFW properly again. Taking into consideration all the warnings, never downgrade first-generation Symbian^3 smartphones using BEST. It is not recommended to downgrade Belle FP2 to Belle FP1 either, despite BEST is the only known way to do that. If you fully comply with the warnings concerned, but still your ultimate decision is to continue downgrading to FP1, then check "DeadMode" box in the "Flashing" tab as well. Moreover, make sure the firmware you are downgrading for contains ENO file. Without it, your smartphone will not boot up.
Czy to oznacza, że można by np. zdowngrade'ować taką Nokię 808 z Belle FP2 do FP1, 701 z Belle FP2 do Belle?
Nie wiem również, jak wygląda sprawa z Symbianami w wersjach niższych od Belle (np. E52).
Jak miałby jednak się odbywać ten cały proces?
1. Tworzy się backup RPL, choć warto zrobić też PM, PP i FullFlash. Jak to zrobić, odsyłam tutaj:
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2. Następnie używa się opcji Full Erase, która czyści praktycznie wszystko w telefonie (pamięć flash, certyfikaty, normalnie wszystko).
3. Przywraca się RPL i flashuje starsze oprogramowanie, z tym, że MUSI ono zawierać plik ENO - do Noki 808, 701 i paru innych można je znaleźć tu:
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Plus parę innych kroków.
Jeden z tutoriali można znaleźć np. na YT: https://www.youtube.com/watch?v=PDfcrENzpbo
Jeśli ktoś ma niepotrzebny telefon z Symbianem i najnowszą wersją softu, może zaryzykować. Nie zmuszam do tego nikogo, gdyż zdaję sobie sprawę, że to ryzykowny pomysł, ale jak się nie spróbuje, to się nie dowie, jak sprawa z tym stoi.
Takie jest moje zdanie. Oczywiście jeśli ktoś uważa, że kolega źle zrobił to wystarczy jedna odpowiedź w temacie z uwagą i już 
