Situation. FED. Starting F1 and F2 swap on 1st trip in 2nd inning. After one batter they swap back on 2nd trip (neither one counted as conference since change made). After one batter they swap again on 3rd trip. I believe they can since pitcher can return to pitch but only once in an inning. Now, is F1 treated the same and he can come back too? I think if he does starting F1 can't come back anymore.

Similar Q. After 3 trips, on the 4th trip you must change, but can starter come back in same inning, and so on and so on or is any pitcher removed due to 4 trips can't come back?