The Flight Pass is a seasonal feature, usually lasting one month. You can level it up by completing daily, weekly, and monthly missions to collect more rewards. In the Flight Pass panel, you can track your progression, see how much time is left until the end of the season, purchase a PREMIUM version of the Pass, and track the rewards granted for each level. It is a time-limited feature, and you need to pick up the rewards unlocked manually to receive them. It is recommended you pick up every reward from the panel when you unlock it, so that you don’t forget to do so before the new season starts.

The Flight Pass Premium is an upgraded, paid version of the regular Pass. It provides significantly more rewards and some new features.

If you were not using the Flight Pass Premium from the start, and you buy it later in the season, you will be able to collect all previously locked rewards up to your current level from the Flight Pass progress panel.

After the end of the season, you need to repurchase the Flight Pass to activate it and to have access to the new season and its rewards. This feature is not a permanent one-time offer, and you need to repurchase it after a specific season ends. The purchase grants you all the rewards that were unlocked during your level progression of the specific season.
It does not give you all the rewards without unlocking the specific level and its rewards.