This is the first time I'm going to use Facebook account kit to verify mobile numbers. My query is, can I verify the mobile numbers that are not linked with any Facebook account ? I have checked all over the internet on this but wasn't able to get any proper answers or responses. Any suggestions on this is much appreciated. Thanks in advance.
You can verify and phone number through Account Kit that has a supported country code (https://developers.facebook.com/docs/accountkit/countrycodes). They do not have to be on a Facebook Account. Accounts created with Account Kit are in no way linked to Facebook Accounts. Instant Verification (referenced in comment above), is used to verify a phone number on a given device, but no link between that Account Kit account and Facebook account is created.