I am not on FB anymore and have never used any of its apps or any other dating apps, so I have no idea; however, you might google it because it seems no one here can help you. I found this on google:
"Facebook Dating is available through the Facebook app on Android and iOS. To access your Dating information, please go to the Facebook app on your mobile device, then go to Access Your Information in your Facebook Settings. If you've added Instagram posts or stories to Dating, learn how to access your Instagram data." And this:
"How It Works
Starting today, you can choose to opt into Facebook Dating and create a Dating profile (separate from your main profile) if youâ€™re 18 years or older and have downloaded the most recent version of Facebook. You will be suggested to others who have also opted in. People are suggested based on your preferences, interests and other things you do on Facebook. Facebook Dating isnâ€™t about swiping or having to wait for someone to like you to get a first chance at reaching out. If you are interested in someone, you can comment directly on their profile or tap on the Like button to let them know. If you arenâ€™t interested, you can pass on them. Facebook Dating allows you to match with friends of friends and/or people not in your friend circle. Facebook Dating wonâ€™t match you with friends, unless you choose to use Secret Crush and you both add each other to your list. All of your Dating activity will stay in Facebook Dating. It wonâ€™t be shared to the rest of Facebook."
And then there's this: https://www.facebook.com/dating/how-to-find/
- it wouldn't let me cut and paste.
So it appears you must sign up for it.
As to your question about how recent these notifications are - you might Google that, too. It doesn't mention anything about that.