The questions were so hard that I got muddled partway through.
Tips
usage
Two readings, two meanings — fāmēng (this entry) = “to be dazed/at a loss”; fāméng (different tone on 蒙) = the older sense “to teach a child to read” (from 启蒙, qǐméng, “enlighten”). In modern speech, the dazed meaning is far more common.
memory
蒙 here originally meant “to cover / to be in the dark.” 发 + 蒙 → “to start being in the dark” → confused. Compare with English “in the dark about something.”