Q: can i change the event photo in photos

Photos does not have events - only albums

If you are talking about the Key Photo for a user made album (not a system album or a smart album) you double click on the photos to enlarge it and press command-shift-K or use the image menu ==> make Key Photo

LN

There are no events in Photos. When you migrated your iPhoto library the events have been replaced by albums, so the event name could be saved. Do you want to change the key photo of these fake event albums?  To set the key photo of an album select the photo while viewing the album and ctrl-click the photo. Select "Make key photo" from the contextual menu.

The "Moments" have replaced the events in Photos. Your library is partitioned into moments, that will be generated automatically, based on the date and the location. You cannot set a key photo for a moment or change the name.

Moments in Photos are the new Events, i.e. groupings of photos sorted by date taken.

When the iPhoto Library was first migrated to Photos there was a folder created in the sidebar titled iPhoto Events and all migrated iPhoto Events (which are now Moments) are represented by an album in that folder. To open the sidebar if it's not already open use the Option+Command+S key combination.

There's a way to simulate events in Photos.

When new photos are imported into the Photos library go to the Last Import smart album, select all the photos and use the File ➙ New Album menu option or use the key combination Command+N.  Name it as desired.  It will appear just above the iPhoto Events folder where you can drag it into the iPhoto Events folder

 

When you click on the iPhoto Events folder you'll get a simulated iPhoto Events window.

The downside to the simulation is that the Albums/Events can only be sorted automatically by Title. But they can also be sorted manually, either in the sidebar or in the folder's window at the right.

Ask Apple for more sorting options in Photos via https://www.apple.com/feedback/photos.html.

can I still do batch name changes in photos or has this been stopped ??

Photos does not support batch changing of titles or descriptions. Perhaps that will change in later versions.

Right now  you can try to use Apple Scripts for batch changing. We posted a few scripts in the User Tip section.

See:  Photos for Mac User Tips