I'm trying to update the fleet from version 3.13 to version 4.0 and vice versa that there are some details that need to be revised. like these: • Change configuration option 

server_tlsprofile

 to 

server_tls_compatability

. This options previously had an inconsistent key name. • Replace the use of the 

api/v1/fleet/spec/osquery/options

 with 

api/v1/fleet/config

. In Fleet 4.0.0, "osquery options" are now called "agent options." The new agent options are moved to the Fleet application config spec file and the 

api/v1/fleet/config

 API endpoint. • Enroll secrets no longer have "names" and are now either global or for a specific team. Hosts no longer store the “name” of the enroll secret that was used. Users that want to be able to segment hosts (for configuration, queries, etc.) based on the enrollment secret should use the Teams feature in Fleet Basic. •

auth_jwt_key

 and 

auth_jwt_key_file

 are no longer accepted as configuration. But when trying to access the link "https://github.com/fleetdm/fleet/blob/main/docs/1-Using-Fleet/8-Updating-Fleet.md" it returns 404 Does anyone have a brief tutorial on how to upgrade from 3.13 to 4.0?

Those docs have been moved to https://github.com/fleetdm/fleet/blob/main/docs/01-Using-Fleet/08-Updating-Fleet.md. The update from 3.13 to 4.x should be relatively smooth, but if you use those APIs you'll need to update. Otherwise, just make sure you either don't use those flags, or you update to the new flag name.