Sorry about the delay in answering your question.
Le Futur antérieur is an indicative tense.
In those examples you have to use it as you are talking about two actions in the future .
After/once you have done this, you will do that.
One action precedes the other and takes the 'futur antérieur'.
In French ( unlike English) words like 'quand', 'lorsque' are followed by a future tense.
Hope this helps!
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