कुत्ते का पट्टा और कॉलर यहाँ हैं।

Because कुत्ता changes to its oblique form कुत्ते before a postposition like का.

• dictionary form: कुत्ता = dog
• oblique form: कुत्ते
• then: कुत्ते का = of the dog / the dog's

This is very common in Hindi. Masculine singular nouns ending in -ा often change to -े before postpositions:

• लड़का → लड़के का
• कमरा → कमरे में
• कुत्ता → कुत्ते का

So कुत्ते का is the normal way to say the dog's.

In Hindi, possessive markers का / की / के agree with the thing being possessed, not with the possessor.

Here, the possessed noun is पट्टा and also कॉलर, and both are treated as masculine singular nouns, so का is used.

Compare:

• कुत्ते का पट्टा = the dog's leash
• कुत्ते की रस्सी = the dog's rope
  because रस्सी is feminine
• कुत्ते के खिलौने = the dog's toys
  because खिलौने is plural masculine

So the logic is:

• possessor = कुत्ते
• possessed items = masculine
• therefore = का

Yes, that is the most natural reading: the dog's leash and collar.

The structure joins two nouns with और:

• पट्टा = leash/strap
• कॉलर = collar
• पट्टा और कॉलर = leash and collar

So the phrase means that both items belong to the dog.

Because one possessive marker can cover both nouns when they are being grouped together.

So:

• कुत्ते का पट्टा और कॉलर
  = the dog's leash and collar

This is natural because पट्टा and कॉलर are part of one coordinated phrase.

If needed, Hindi can repeat the possessive marker for clarity or emphasis, but it usually does not have to here.

Because the subject is effectively plural: पट्टा और कॉलर = the leash and collar.

Even though each noun is singular by itself, together they form a compound subject, so Hindi uses the plural verb:

• पट्टा यहाँ है। = The leash is here.
• कॉलर यहाँ है। = The collar is here.
• पट्टा और कॉलर यहाँ हैं। = The leash and collar are here.

So हैं matches the combined meaning are.

A natural literal breakdown is:

• कुत्ते का पट्टा और कॉलर = the dog's leash and collar
• यहाँ = here
• हैं = are

So the sentence is roughly:

The dog's leash and collar here are.

That sounds odd in English, but it is normal Hindi word order. Hindi often puts the verb at the end.

A helpful pattern is:

[subject] + [place/time/etc.] + [verb]

So here:

कुत्ते का पट्टा और कॉलर + यहाँ + हैं

Yes, Hindi allows some flexibility.

These can all sound natural, depending on emphasis:

• कुत्ते का पट्टा और कॉलर यहाँ हैं।
• यहाँ कुत्ते का पट्टा और कॉलर हैं।

The version you were given is very normal and neutral.

Putting यहाँ earlier can emphasize the location a bit more, something like Here is where the dog's leash and collar are.

It is a borrowed word from English, and Hindi uses many such loanwords in everyday speech.

So कॉलर is a very normal Hindi word in practice, even though its origin is English.

Hindi often mixes native words and borrowed words naturally:

• पट्टा = native/common Hindi word
• कॉलर = English loanword used in Hindi

This kind of combination is completely normal in modern Hindi.

Here it is singular: of the dog.

That can be confusing because कुत्ते can look like a plural form in other situations. But in this sentence, the following का tells you that कुत्ते is the oblique singular form of कुत्ता.

So:

• कुत्ता = dog
• कुत्ते का = of the dog / the dog's

If you wanted of the dogs, you would normally say:

• कुत्तों का = the dogs'

Because Hindi does not have articles like a, an, and the.

Hindi usually leaves that information to context.

So:

• कुत्ते का पट्टा can mean the dog's leash
• depending on context, Hindi does not need a separate word for the

This is very normal. When translating into English, you add the if the situation makes it definite.

Yes. That is an excellent natural translation.

A very literal word-for-word version would be:

• कुत्ते का = the dog's
• पट्टा और कॉलर = leash and collar
• यहाँ = here
• हैं = are

So the full sense is:

The dog's leash and collar are here.

Yes, you could also say:

कुत्ते का कॉलर और पट्टा यहाँ हैं।

That would still be grammatical and would mean the same thing. The difference is mainly emphasis or style.

The original order may sound a little more natural if the speaker happens to think of पट्टा first, but both are fine.