Fedora Linux 34 will go end of life for updates and support on 2022-06-07.
No further updates, including security updates, will be available for Fedora Linux 34 after the said date. All the updates of Fedora Linux 34 being pushed to stable will be stopped as well.
Fedora Linux 35 will continue to receive updates until approximately one month after the release of Fedora Linux 37. The maintenance schedule of Fedora Linux releases is documented on the Fedora Project docs site . The Fedora Project docs also contains instructions  on how to upgrade from a previous release of Fedora Linux to a version receiving updates (Fedora Linux 36 or Fedora Linux 35).