| John Mechalas |
"See above", meaning, the answer "no" to the first implies the answer to the second.
You can dismiss blink, but when the spell ends you return to the plane you were on when you cast it. While this isn't explicitly stated, the convention with spells that have a duration is that the effect ends when the spell does.
If it let you switch permanently between one or the other by timing the dismissal just right, you'd essentially have a very cheap version of Plane Shift.