I want to know the answer to the following question:
What did the old letter ⟨ѳ⟩ become?
All the background I'm provided with is that "Older letters of the Russian alphabet include ⟨ѣ⟩, which merged to ⟨е⟩ (/je/ or /ʲe/); ⟨і⟩ and ⟨ѵ⟩, which both merged to ⟨и⟩ (/i/); ⟨ѳ⟩, which merged to ⟨ф⟩ (/f/); ⟨ѫ⟩, which merged to ⟨у⟩ (/u/); ⟨ѭ⟩, which merged to ⟨ю⟩". Is that enough to answer the question?
Answer: yes