Were Paul's letters already written and circulated when Peter wrote 2 Peter?
Paul's letters had already been written for the most part when Peter wrote 2 Peter, around A.D. 65–67. They may not all have been circulated widely yet, but they had been written. Peter references Paul's writings, indicating they were known and available to his readers.
Les explains that Peter wrote these epistles shortly before his martyrdom, around A.D. 65–67, before the temple was destroyed in A.D. 70 and Israel went out into dispersion. He notes Paul's letters had already been written for the most part, though they may not all have been circulated that much yet. In 2 Peter 3:15, Peter calls Paul "our beloved brother" and acknowledges that Paul wrote according to the wisdom given unto him. Peter also writes that the long-suffering of our Lord is salvation, not willing that any should perish.
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Had Paul's letters been written by the time Peter wrote 2 Peter?
By the time Peter wrote near the end of his ministry, Paul's letters had already been written for the most part, though they had not all been widely circulated yet.