UEFA, as far as I know, don’t allow any separate side clauses like this so I’d say he’ll be eligible. Same way Roberts played against Manchester City last season and Celtic had to face Mo Bangura when he was on loan with a Swedish outfit a few years back.
I saw €10m quoted for the buy option. I think this is good forward planning, bhoys. A year to settle in and overlap with Dembélé. If he’s shit, he goes back. If he’s good, he gets bought for around 25% of what we’ll get for Dembélé.