You will see the Conectado (Connected) chip and your numbers under Números conectados.
The "Enviar blast masivo" (Send bulk blast) button is enabled when the Preparación para Envío de Mensajes (Messaging readiness) card shows the required checks in green and you have successfully sent a message with "Enviar Mensaje de Prueba". That test uses an approved template with no variables or media: keep at least one like that.
Yes. AFRUS warns you with "Tu conexión expirará en N días"; when it expires, click "Reconectar con Facebook".
In Meta's Phone Manager. Then click "Sincronizar con Meta" (Sync with Meta) in AFRUS.
The number is still linked to another WhatsApp account. If it has WhatsApp or WhatsApp Business on a phone, in the app go to Settings > Account > Delete account (uninstalling the app is not enough). If it was connected to another WhatsApp API provider or to another Meta account, ask them to disconnect it and turn off the two-step verification PIN. Then wait a few minutes and try again from AFRUS.