Italian usually uses the definite article more often than English.
Here la casa simply means the house. Since casa is a singular feminine noun, it takes la.
Article + noun:
If you removed the article and said just casa, it would usually sound incomplete in this kind of sentence.
No. The infinitive is appartenere.
Appartiene is the third person singular present tense form, used with la casa:
Since la casa is singular, you use appartiene.
That is the normal structure with appartenere:
La casa + appartiene + a mia sorella
Italian word order is often similar to English here. The thing being talked about comes first, then the verb, then the person it belongs to.
You could change word order in special contexts for emphasis, but this sentence is the standard, neutral order.
Usually, in a neutral statement like this, you say mia sorella.
Sorella mia is possible, but it is more expressive, emotional, literary, or emphatic, somewhat like saying my dear sister or stressing the relationship.
So here the normal choice is:
It is pronounced approximately like:
ap-par-TYE-ne
A more careful breakdown:
The stress falls on tie: apparTIÈne
If helpful, the infinitive appartenere is stressed differently: apparteNÈre
You would normally use an indirect pronoun:
Here:
Other forms:
In everyday speech, Italians often choose a fuller form if needed for clarity:
No. It can also mean to belong to in the sense of being part of a group or category.
For example:
In your sentence, though, it is about possession or ownership.