A repository uses repository custom instructions to reduce drift during long Copilot sessions. The team also requires a PR checklist that records the original issue, accepted scope, changed files, and validation commands. Evaluate the following statements. 1. The instructions help preserve task state across a longer agent session. 2. The checklist can help reviewers detect drift before merge. 3. The instructions guarantee Copilot cannot modify unrelated files.

Statement 1 is correct because the repository custom instructions, particularly "If the task scope changes, ask for maintainer confirmation in the issue or PR," guide Copilot to acknowledge and potentially halt for scope changes, effectively preserving the task state by preventing unapproved deviations during extended sessions. Statement 2 is correct because the PR checklist explicitly includes "Changed files reviewed against accepted scope" and "Scope changes approved by maintainer," which directly prompts reviewers to verify that the changes align with the original intent and accepted scope, thus helping detect drift before merging. Statement 3 is incorrect because instructions are guidelines for Copilot's behavior, not guarantees. While the instruction "Keep implementation limited to files named in the accepted scope unless the PR explains why more files changed" aims to restrict changes, Copilot is an AI assistant and can still modify unrelated files if its model determines it's necessary, or if the instructions are not sufficiently precise or overridden by other factors. It does not enforce a hard technical constraint.