I have some webparts who have dependency of data which is obtained from application customizer. Is it possible to load webparts after application customizer
What you want to do is use a state management approach. In React, you can use Redux or MobX (and others) as your state management solution.
So, in MobX, for example, your web part would subscribe to an observable, and when that observable changes - your data from the application customizer, for example - then your web part can grab it and do what it needs to do.
If your requirements is , you want to execute your Spfx extension - oninit method after loading your other web-part or add-ins in your page .