Is it possible to take back one's wife after the husband has uttered the divorce three times consecutively, and a divorce decree has been issued to that effect, knowing that approximately three and a half years have passed since the divorce?

The relied-upon fatwa is that the statement "You are divorced, you are divorced, you are divorced" effects a single divorce if the reiteration was not intended to effect more than one. It effects three divorces if three were intended. If nothing was intended, then it is a single divorce. The wife could have been taken back before the 'iddah expired. If the 'iddah expired without reconciliation, the wife became irrevocably separated, and a new contract is required for her return.