Can the Senate confirm a SCOTUS nominee before the seat is vacant?

The media is reporting that Justice Stephen Breyer plans to retire at the end of this year's court term.

Senate Majority Leader Chuck Schumer issued the following statement regarding the confirmation process.

President Biden’s Supreme Court nominee will receive a prompt hearing in the Senate Judiciary Committee and be considered and confirmed by the full United States Senate with all deliberate speed.

So, since Justice Breyer has not officially retired from the court, can the Senate confirm a President's nominee at this point of time?

Can the Senate confirm any federal judges or Cabinet positions when the incumbent has not vacated the position, for that matter?

If so, what's stopping the Senate from erroneously confirming judiciary nominees for seats that aren't vacant?