The most serious errors here:
When Alan comes home, he usually has a sandwich.
When Alan comes home, we will talk about it.
The subordinate clause is adverbial in both!
2) “When I graduated” modifies me.
No, it modifies 'day'! (The word 'me' does not even occur in the sentence!!)
3) In the first example, “He usually has a sandwich” modifies Alan.
It is a contradiction in terms to speak of a main clause 'modifying' anything!!!
You seem to be inviting an honest response, and so, for your sake and that of your students, I trust you will not take offence at my offering one: I have rarely seen such a collection of fundamental errors and misconceptions about English grammar crammed into the space of a single post. What makes things far worse is that this is apparently being offered up as instructional material!
If the above is indicative of your level of understanding of grammatical terms and concepts, I would seriously advise you to give up teaching grammar altogether!!