Is there anything to protect against parallel construction? Bob mentions he was selling drugs to a guy near the scene of the crime. A police officer then finds out who the buyer was, and gets him to testify to bring drug charges against Bob. Or: During the following weeks, a police officer just happens to be in the same place at the same time of night every week, and eventually catches one of Bob's future transactions.

https://en.wikipedia.org/wiki/Witness_immunity seems to be the reference. Seems to cover the exact issue: "In the United States, the prosecution may grant immunity in one of two forms. Transactional immunity, colloquially known as "blanket" or "total" immunity, completely protects the witness from future prosecution for crimes related to his or her testimony. Use and derivative use immunity prevents the prosecution only from using the witness's own testimony or any evidence derived from the testimony against the witness. However, if the prosecutor acquires evidence substantiating the crime independently of the witness's testimony, the witness may then be prosecuted."

Could you have committed an unrelated murder, and by disclosing this murder in your testimony, become immune to conviction of it?

If that is not how immunity works, then how can the government force anyone to testify? The government does not know what (unrelated) crimes I may have to confess to in order to give truthful testimony on the matter in question.

Does that include false testimony? If so, why couldn't Manning employ the Regan/Poindexter tactic... I don't recall? Or can the immunity be rescinded if the testimony doesn't produce the answers the prosecution wants?