“Do you think it is possible, for a normal human being (without magga phala), to act like an arahant on a certain occasion?”
If you mean whether a normal person can act wisely in a certain situation, yes.
“Is his/her behaviour always driven by abhisankhara, avijja and tanha/”
No. It is under “tempting situations” one acts like that. It depends on one’s anusaya.
“It is possible a normal person can act occasionaly with punna kiriya? ‘
Of course.
“Is purity of mind something that cannot be present in a normal person on a certain moment?”
There is no “fixed” mind. Mind (or more correctly thoughts or citta) arise when an external sense input comes in through one of the six senses, including the mana indriya.
See, “Do I Have “A Mind” That Is Fixed and “Mine”?”
“Is purity of mind something that cannot be present in a normal person on a certain moment? Can a normal person act with wisdom. ”
Yes.
Also see, “‘Self’ and “no-self”: A Simple Analysis – Do We Always Act with Avijja?“