Hello Mohammed,
I hope you are doing great,
I really want to understand what kind of failover scenario you are looking for, if the extreme switch is a L3 switch which happens to support ant FHRP protocol such as VRRP then you can have redundancy and failover scenario with no problems with a 3850 switch which uses IOS-XE.
If you are looking for a L2 redundancy that most likely works with Stack wise type technology which is only between cisco switches.
Now please explain what kind of failover you are looking for, if you dont mind.
Please proceed to rate all helpful posts and mark as answered if this was the right answer for your question,
David Castro,