Learn English – Using “now” with the future tense

SHORT ANSWER:
Only your first sentence is idiomatic English.

LONG ANSWER:
First, will is employed in when clauses only if when is employed as a relative adverb, not if when is employed as a subordinating conjunction:

 You will arrive in Milan at 4 pm, when you will be met by our representative.
^✲When you will arrive in Milan you will be met by our representative.

Second, the ‘sequence of tenses’ rules for sentences with [when] ... [then] and [if] ...[then] constructions are very similar, so I’ll treat them together.

NOTES: I bracket [when], [if] and [then] because these words may only be implied and not actually appear in a sentence. Also, I have changed the words in your example to permit what I hope is a more transparent explanation.

The rules vary depending on whether the sentence expresses habitual practice or, as in your example, a single contingency.

1. If the sentence expresses a repeated or habitual practice, both clauses will have the same tense: either simple present or simple past. In these cases, [when] or [if] bears the sense whenever.

   [Our practice is: ] Whenever we see this, we do that.
   [Our practice was:] We did that whenever we saw this.

2. When the sentence deals with a single occasion, English employs a sequential structure, in which the [then] clause is depicted as ‘following’ the [when] or [if] clause. In practice this means that

   • In sentences with present reference, a simple present or present perfect in the [when/if] clause is paired with a will + unmarked infinitive construction in the [then] clause.

     NOTE: 1) The order of the clauses in the sentence is irrelevant, and 2) I speak of a ‘construction with will’ rather than of a ‘future tense’ because the will signifies consequence quite as much as it does futurity.

     [We have decided:] If we see this, we will do that.
     [We have decided:] We will do that when we have seen this.

   • Sentences with past reference are ‘backshifted’: a simple past or past perfect in the [when/if] clause is paired with a would + unmarked infinitive construction in the [then] clause.

     [We decided yesterday:] If we saw this, we would do that.
     [We decided yesterday:] We would do that when we had seen this.

The continuous form is used to state or ask what was, is or will be happening at a given moment. So, if you call your friend and ask: What are you doing? she may answer: I'm playing cricket (for example, she is standing on the boundary with her phone in her pocket when you call).

If you tell your friend that you intend to call her around 7pm tomorrow, she may reply: Sorry, but I'll be playing cricket. In other words, around the time that you plan to phone, she will be on the cricket field and unable to take your call. (The simple future I will play cricket is not possible in this context.)

In the passive form, the object is made the subject or topic of the sentence. So in a context where sports are the subject of discussion, the passive is just about conceivable.

Which sports will be being played after school tomorrow?

• Cricket will be being played by me.

• Tennis will be being played by John.

• Badminton will be being played by Mary.

But as Parrott in Grammar for English Teachers (p336) states:

Some people dislike putting two forms of be together (e.g. be being or been being) ... They avoid standard passive constructions in the future continuous or predent perfect continuous.

Perhaps you could ask your friend why he or she changed your perfectly usual statement into one that would be perceived by native speakers as extremely odd. It would also be useful to link to the BBC English page referred to in the question.