How do I determine whether specific message in Messages is Fraud?

It is a SCAM! Do not click links or provide personal information from Messages. Facebook is especially known for the scams that would be sent to you using the Messenger app. If you have already provided personal account information, you will need to follow up to change your Passwords and secure any account.

It's 100% a scam

Literally, ANY too-good-to-be-true offer that comes via text/Messenger/Telegram/WhatsApp, especially one that needs you to pay up-front to receive whatever snake oil they're peddling, is a scam.

Did you even apply for a federal grant? If you didn't, why would they be offering you one (they don't just hand them out willy-nilly via Facebook), and if you did, you'd know the formal grant application/approval process (hint: it doesn't involve Facebook Messenger)

Hello~ It’s a total scam…please don’t interact with that at all. Click on below to see what Apple has to say…

Recognize and avoid social engineering schemes including phishing messages, phony support calls, and other scams - Apple Support

Also if you gave any personal information…

If you think your Apple Account has been compromised - Apple Support

~Katana-San~