1) On Rosh Hashanah one may only blow the shofar in order to fulfil one’s obligation, or to allow someone else to fulfil their obligation. It is forbidden to blow for another reason even if he is blowing on the first day in order to learn and practice for the second day. (Kitzur Shulchan Aruch 129)
2) One who has already fulfilled his obligation to blow the shofar and comes to blow for someone else who has not yet fulfilled his obligation, may make the blessings for him. It is, however, better that the listener, who is now fulfilling his own obligation, should make his own blessing. However, if he is lowing to allow women to fulfil their obligation, he may not make the blessings as since according to the strict letter of the law women are not obligated to fulfil this commandment, as it is time-related, just a woman may listen and make the blessing, it follows that she should make the blessing herself. (This is only according to the Ashkenazy custom that women make blessings even on positive time-related commandments.) (ibid)
