Is there any difference between the two idioms, "one-to-one" and "one-on-one", when the meaning is 'between only two persons'? Can they be used interchangeably, for instance, in the following situations?
1. The pastor had a one-to-one session with the family discussing its problems.
2. The lecturer preferred the one-on-one meetings with his students.
3. The father had a frank one-to-one discussion with his children.
4. Do not miss the chance to meet the President one-on-one.
5. The monk mentioned this during his one-to-one class with his disciples.