After Hint 4, it seems we need to
convert the given letters into symbols for elements on the periodic table. Since this doesn't make sense when reading forwards, we go backwards instead.
The letters are then:
Eu Md Ir Db Pb Es Ge Tb
Ge Lv Au Ds Ge Yb Rg Ge Ir
Bk Pb Lr Tb Ds Tb Ge Ds Tb
Ge Uup Ta Ge Md Pb Uus Po
Bk Tm Fl Ho Ge Hs Tb Es Ta
Lr Tb Mt Ge Hf Es Ta Rf Fr
Next step:
convert them to their numbers in the periodic table:
63 101 77 105 82 99 32 65
32 116 79 110 32 70 111 32 77
97 82 103 65 110 65 32 110 65
32 115 73 32 101 82 117 84
97 69 114 67 32 108 65 99 73
103 65 109 32 72 99 73 104 87
The next step (thanks @user3574641) is to
convert these numbers using ASCII:
? e M i R c A
t O n F o M
a R g A n A n A
s I e R u T
a E r C l A c I
g A m H c I h W
i.e. "Which magical creature is an anagram of NOT A CRIME?"
to which the answer is (thanks @hagfy)
MANTICORE.
Feedback section
The puzzle was very well put together, with many different steps leading inexorably to the solution. However, I think the cluing of exactly what to do could have been done better. Hints 3 and 4 combined make it very clear what to do, and Hint 4 would probably be enough on its own, but the puzzle should be self-contained even without added hints. It would have been better to add a bit of flavour text with some subtle cluing in that direction, rather than posting the image without context and then adding spoilertagged hints later.