Lol Ao is sitting still looking pretty http://www.mangago.zone/read-manga/akatsuki_no_yona/an/d_v-28-chapter-166/pg-30/
Hmm wat if Arhad with memories and Arhad in her school right now are actually different ppl. Like a twin perhaps? or multiple personality that flares once in a while (where other personality have the memories?)
Highly unlikely because he has the past memories ingrained into him which can probably cause some impulse reactions like how Ianna acted when she demanded for arhad's schedule. Plus, your personalitys bound to change when you have your past memories, for example, like Ianna. Her choices in this "timeline" paved way towards a different path extremely different from her "past self" . Of course it may still be following the same timeline from the "past timeline" but in this "restart" of her life, she did find out that she had roberstein in her and did meet everyone earlier than expectex. Soooo, yeah I don't think his memories flare up and stuff. I think his wonky behavior is caused by his unsureness on how to approach and interact with Ianna in order to stray from the "past timeline" where he isn't killing her. Plus, he doesn't see her as different from her "past self" when she's charging in like a bull and wanting to spar .
Just my deduction from re-reading this story several times
Translator come out and meet me I promise I won't bite you (╹◡╹)♡