No. LG K9 Candy does not have the front camera LED flash but it does have the display flash. Which helps to take a good selfie during low light conditions.
No. LG K9 Candy does not have the fast charging support. But if you charge with the original charger and cable which is supplied, the phone gets charge very quickly.
Yes, LG K9 Candy does have the FM radio.
Yes, LG K9 aka LG Candy is a 4G mobile phone.