I create slideshow in Photos

I am seeing the TV.app in the Applications folder. You will find the Applications folder directly on your Macintosh HD, together with all your other applications. TV is one of the successors to iTunes, where we are supposed to collect all movies. I do not use an TV, so I hope, someone else will answer your questions about using your TV.

To write the , you can use the Character Viewer. You can launch fro "Edit > Emoji & Symbols". when the palette opens click the tiny palette to the right of the search field. You have to customise it to include all unicode characters. The  is in the Private Use Area, under F8FF. Once I found it, I added it to the favorites.

Which version of Photos and MacOS X are you using?

When you save slideshow in Photos 5 on Catalina by clicking the "Export" button, you can select the folder in the Export dialog. By default, the video will be saved in the "Movies" folder.

You can add it to the TV.app by launching TV, then use the command "File > Import" and select the exported video.