STIHL BR800 C

Hi all, I’ve been a complete idiot and put 4 stoke Aspen fuel In my (second hand, but relatively new) 2 stroke/ 4-mix BR800 C. It ran ok for about an hour. then a week later when I released my mistake i drained tank and replaced with Aspen 2 stroke it ran for 10 minutes, died, and now will not restart. Can someone tell me honestly, have I ruined the whole engine? Is there any way I can fix my mistake? I know I’ve been an idiot so go easy,