je vs jouw

[yapaxi]

Is there a more or less common real world example of possessive "je" when the possessiveness is not stressed so actually "je" can be used instead of "jouw"?

For instance:
- hoe doet jouw hond dat? (it is clear that "je" is stressed)
- hoe doe je hond de truc? (is it still stressed even if I put emphasis on the trick?)
- doe je hond aan de riem (probably not stressed but not really possessive, more like categorical)

[LeSNT2]

Is there a more or less common real world example of possessive "je" when the possessiveness is not stressed so actually "je" can be used instead of "jouw"?

For instance:
- hoe doet jouw hond dat? (it is clear that "je" is stressed)
- hoe doet je hond de truc? (is it still stressed even if I put emphasis on the trick?)
- doe je hond aan de riem (probably not stressed but not really possessive, more like categorical)

I'm not sure if I understand your question correctly but 'je' is never stressed. The stressed form is always 'jouw', 'jou' or 'jij'.

So:
Is dat jouw boek? = stressed
Is dat je boek? = unstressed (I would say the stressed part would be 'dat' in this case or 'boek')

Any time you don't want to stress the possessive part, you can use 'je' it's one of the most used words in Dutch.

And 'doe je hond aan de riem' is possessive, it's still about 'your dog' not any other dog.

[yapaxi]

Is dat jouw boek? = stressed
Is dat je boek? = unstressed

What I am trying to understand here is if choice of jouw \ je is required by grammar or is it always up to me?

Like:

1) I have to use "jouw" because there is no way to use possessive without stressing the owner's pronoun.

2) OR

Is dat jouw boek?

It is more about the owner than about the book, so maybe the book is occuping the chair and I wonder if the owner can remove it.

Is dat je boek?

It is more about the book than about the owner, so maybe I am casually asking if I can quickly check it.

[BrutallyFrank]

I think that you're right about these words being stressed: jouw (stressed), je (more casual). But the problem is that stressed/unstressed is mostly clear when the words are pronounced. In that case you can actually give these sentences three different meanings:

Is dat JOUW boek? - and not somebody else's? (possession/ownership)
Is dat jouw BOEK? - or is it something else? (what is it?)
Is DAT jouw boek? - Is it that book and not that other one? (distinguish between objects)

If you don't want to stress anything, you can use both je and jouw, if you need to know about the ownership you use 'jouw' and also stress it when pronounced.

[LeSNT2]

It's always up to you (and the context).

Is dat jouw boek?

It is more about the owner than about the book, so maybe the book is occuping the chair and I wonder if the owner can remove it.

Indeed, it's more about the owner than about the book. Your example about occupying the chair would be correct. Or for example when you wrote a book and I didn't know you're an author, I could say: "Is dat jouw boek?"

Is dat je boek?

It is more about the book than about the owner, so maybe I am casually asking if I can quickly check it.

Indeed, it's more about the book than about the owner. For example: I know you're an author but I thought you wrote another book, I could say: "Is dat je boek?" (maybe with a little stress on 'dat'). Or if I'm not sure if I'd heard you correctly, maybe we're talking about pants (broek in Dutch) and you say something about 'boek' I could say: "Is dat je boek?" with a little stress on 'boek' (because I think you need to say 'broek' instead of 'boek' in this context).

Hope this helps. Ask further if you don't fully understand yet!