2 questions

[bayan said]

It`s bayan again,this time I`d like to ask 2 questions,thanks in advance:
A- I`ve read the following text & I have some questions on it" - our gran`s visiting us next week-How long is she staying?-she`ll be with us from Monday to friday.we`re going to do a lot of things.she`ll probably take us to the cinema on monday evening.And she`s going to take us to a pop concert on thursday.And on Wednesday she`s probably taking us roller skating"
1- why did we say "how long is she staying?instead of how long will she be staying?.
2- why is the simple future used here"she`ll be with us from monday to friday?although she said"from monday to friday"then it is a specific time then she isn`t guessing.
3- why did the speaker say"she`ll probably take us to the cinema on monday evening"although there`s a specific time?
4- why did the speaker say"she`s going to take us to a pop concert on thursday"although in the pervious sentence the simple future is used?
5- why did the speaker say " she`s probably taking us roller skating on wednesday" although "probably"is used? for I`ve read that with words like "probably,maybe" the simple future is used...
6- and finally there`s a practice about choosing the correct tense :" I hear your brother is going to university later this year.what( is he studying/is he going to study)? & why?
B- I`ve read thise sentence" the bank`ll need an example of your songs befor they`ll accept your cheques"why is "will" used in the sentence"befor they`ll accept your cheques"although the clause begins with "befor"?

[Tdol]

1 You could use 'will be staying' too. The present progressive is used to show a fixed arrangement.
2 I think that it sounds better with the verb 'be', instead of using the present, though with another verb, you could say 'is staying'.
3/5 Because it's 'probably', so it's not an arrangement.
4 It's an arrangement
6 I'd used 'going to' because we don't know for sure until the person answers whether it is definite.