I know I am not Catorce, but I will try to answer some questions
In the practice match against Werder Bremen, both Fischer and Bojan played. Fischer played as a left winger, the position he always plays in. Bojan played as a right winger. De Boer will prioritize using Fischer, because he actually belongs to the club (Ajax own Fischer), unlike Bojan (because he is on loan), and because they are very similar players, style-wise and quality-wise. Bojan will just be some sort of backup I guess. He will probably play RW most matches.
Boilesen has been injured for almost 2 years, but during that period, he has gained 8 kilograms of weight/muscle without losing speed, he said recently. Frank de Boer recently said Boilesen 'has become a man.' Last season, Dayley Blind took the spot of Boilesen as a left back and Blind even made it to the Dutch national team, because he played very well. Right now, Blind will probably be the regular starter and not Boilesen, because Boilesen hasn't played in a long time. However, he sure is and was a good player, so he might be able to become the 1st choice again.
I haven't seen Andersen play to be honest, mainly because he has only made a few appearances for the first team of Ajax. I do think the time is right for de Boer to start using him more often. The problem for Andersen is that Ajax has a lot of forwards and midfielders.
Excuse me for my bad english
EDIT: I don't support Ajax either so I don't know a hell of a lot about the club.
When I watch Dutch football I am pretty much a neutral spectator