Yes, you will have to create a custom policy for that, and then:
1: Declare the "ageRange" and "gender" claim types in the extension file.
2: Add both the "age_range" and "gender" fields to the "ClaimsEndpoint" metadata item and the "ageRange" and "gender" output claims to the "Facebook-OAUTH" technical profile.
3: Issue the "ageRange" and "gender" claims in the relying party file.
If you are wanting to save the "age_range" and "gender" fields from Facebook as attributes to Azure AD B2C, then you must:
1: Follow the Azure Active Directory B2C: Creating and using custom attributes in a custom profile edit policy steps to create the custom attributes for "AgeRange" and "Gender".
2: Change the claim type declarations, as well as all other references to them, from "ageRange" and "gender" to "extension_AgeRange" and "extension_Gender".
3: Add the "extension_AgeRange" and "extension_Gender" claims in the extension file to the "AAD-UserWriteUsingAlternativeSecurityId" and "AAD-UserReadUsingAlternativeSecurityId" technical profile:
<ClaimsProvider>
<DisplayName>Facebook</DisplayName>
<TechnicalProfiles>
<TechnicalProfile Id="AAD-UserReadUsingAlternativeSecurityId">
<OutputClaims>
<OutputClaim ClaimTypeReferenceId="extension_AgeRange" />
<OutputClaim ClaimTypeReferenceId="extension_Gender" />
</OutputClaims>
</TechnicalProfile>
<TechnicalProfile Id="AAD-UserWriteUsingAlternativeSecurityId">
<PersistedClaims>
<PersistedClaim ClaimTypeReferenceId="extension_AgeRange" />
<PersistedClaim ClaimTypeReferenceId="extension_Gender" />
</PersistedClaims>
</TechnicalProfile>
</TechnicalProfiles>
</ClaimsProvider>