Bat Mitzva (2)

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Question
Why don't fathers recite ברוך שפטרני at their daughter's bat mitzvahs? Is this a brachah just for the father or should a mother also be saying the bracha at her sons' bar mitzvahs? Do we assume all the sins of the son goes to the father (and not the ...
My daughter and I will be completing a masechet of Gemara and are planning to make a siyum at her bat mitzva celebration. There will be at least 10 male guests. After she says the hadran, should the Kaddish be recited and by whom?