Following up on http://dinonline.org/2017/01/05/davening-again-because-one-had-to-use-the-bathroom/:
Would the same apply (that he may not answer Kedusha or talk) even if we are talking about one who went to the facilities during Mincha, where there is no need to adjoin geula to tefilla?
Also, if one already began to bless asher yatzar (which according to rav’s response is assur), should he complete the benediction, or stop immediately as seemingly he is in the middle of SE?
The sources that I quoted are talking about all SE, because right now he is like in middle of davening, so it would be also by mincha.
Regarding your second question, although one should not say asher yatzer, if he started it already, he should not stop now and also cause a bracha levatala