The "t" is there for purely phonetic reasons to prevent the two vowels from clashing.

In the lesson linked to your question I couldn't find where it says that où must be followed by inversion.

The three ways to ask the question::

Où je mets mes chaussures? or Je mets mes chaussures où?
Où est-ce que je mets mes chaussures?
Où mets-je mes chaussures?

Yes, that's correct.

Yeah i know. I didn't know how to cancel the question! Anyway thanks for answering me

Thanks! Are they correct those?

Elle est comment, la cantine?

Elle arrive quand, la neige?

Il serait oú, mon boureau?

Oú elle est, la poulette?/Elle est oú, la poulette?

I have found these questions on internet, but i never saw this type of construction..Are they right?

If I wanted to know when the church was built, I would use one of those possibilities:

1) L'église a été construite quand?

2) Quand l'église a-t-elle été contruite?

3) Quand est-ce que l'église a été construite?

Thanks? And are those correct? Cause i never saw this construction on internet?

Elle est comment, la cantine?

Elle arrive quand, la neige?

Il serait oú, mon boureau?

Oú elle est la poulette?

Elle est oú, la poulette?

Salut Cecile

I thought that in the 3rd person plural in the present tense, the "ent" was never pronounced.

Ils tombent  would sound tombe

Ils chantent  would sound chant

Ils regardent, etc.

Forgot to tick to recieve your response.

Merci beaucoup

Bonjour Madame Cécile !

I would like to post a follow-up as I am facing a confusion-

A sentence is provided- John et Pauline vont à l’école tous les jours.

To form a question would we write-

Qui vont/va à l’école tous les jours ?                                                 

Does “qui” always require a verb in third person singular ?         

This was mentioned in the answer to the following question -

https://progress.lawlessfrench.com/questions/view/use-of-il-form

If so, then the answer to my original question should be-

Qui es ton ami ?

Merci encore pour votre aide continuel.

Bonne journée !

Merci encore Madame !

Just to clarify my learning ->

If a teacher wants to say- Who is talking while I am teaching ?

Then, “qui” will be followed by a third person singular verb -> Qui bavarde pendant que j’enseigne ?

And, if my mother asks- Who are coming to attend your birthday party ?

Here also , “qui” requires a third person singular form as qui is the subject of the verb -> Qui vient assister à ta fête d’anniversaire ?

Is it possible to say Oú est la chair?

Thanks and are they correct these sentences?

Oú est -elle?

Oú elle est?

Oú se trouvent les filles?

Oú elles se trouvent?

Oú sont- ils?

Oú sont les filles?

Thanks and are those right?

Oú est-elle?

Oú elle est?

Oú se trouvent les filles?

Oú elles se trouvent?

Oú sont-ils?

Oú ils sont?

Oú sont les filles?

Thanks! Are they correct those?

Elle est comment, la cantine?

Elle arrive quand, la neige?

Il serait oú, mon boureau?

Oú elle est, la poulette?/Elle est oú, la poulette?

The question words are always placed at the start in the inverted question form.

Quand ouvre-t-on les cadeaux?

The "t" is just interposed to prevent two vowels from clashing, is all. Nothing deep, no reference to anything grammatical. sometimes things really are simple ;))

-- Chris. 

"Comment allez-vous?" Should do the trick. The inverted form is the one I hear most often used. 

-- Chris. 

Yes, it is "où êtes-vous?" (Note the hyphen in the inverted form). 

-- Chris (not a native speaker).