Her dinin farklı kuralları var.

Because her means every or each, and in Turkish it is followed by a singular noun.

• her din = every religion
• not her dinler

This works much like English:

• every religion
• not every religions

So even though the meaning is plural overall, the noun after her stays singular.

Dinin is din plus the genitive ending -in.

• din = religion
• dinin = of the religion / religion's

Turkish often shows possession with a two-part structure:

X-in Y-si = X's Y / the Y of X

So here:

• her dinin = of every religion
• kuralları = its rules / the rules

Together, her dinin farklı kuralları literally means something like every religion's different rules.

Because in this kind of possessive structure, the possessed noun also needs a possessive suffix.

So the pattern is:

• dinin kuralları
• literally: the religion's rules

Breakdown:

• kural = rule
• kurallar = rules
• kuralları = its rules / the rules of it

Here, -ları is not just a simple plural ending. It contains:

• -lar = plural
• -ı = 3rd person possessive

So kuralları means its rules in this sentence.

Yes, by itself kuralları can be ambiguous.

Depending on context, it can mean:

• his/her/its rules
• their rules
• sometimes even their rule in other contexts

But in this sentence, the previous phrase her dinin makes the meaning clear: it means the rules of each religion.

So context removes the ambiguity.

Turkish usually expresses possession with var and yok, not with a direct verb like English to have.

A very common pattern is:

X-in Y-si var = X has Y X-in Y-si yok = X doesn't have Y

So:

• Her dinin farklı kuralları var.
• literally: Every religion's different rules exist.
• natural English: Every religion has different rules.

This is one of the most important patterns in Turkish.

For example:

• Benim bir arabam var. = I have a car.
• Onun vakti yok. = He/She doesn't have time.

Because Turkish adjectives do not change for number, gender, or case.

So farklı stays farklı no matter what noun comes after it:

• farklı kural = a different rule
• farklı kurallar = different rules
• farklı din = a different religion
• farklı dinler = different religions

Unlike in some languages, Turkish adjectives do not agree with the noun.

Yes, that is grammatically possible, but it changes the feel of the sentence.

• Her dinin farklı kuralları var = every religion has different rules / multiple rules
• Her dinin farklı kuralı var = every religion has a different rule / some distinct rule

The plural kuralları is the more natural choice if you mean that religions generally have multiple rules.

Yes. Vardır is correct.

Difference in tone:

• var = neutral, common, conversational
• vardır = more formal, more written, sometimes more like a general truth or assertion

So both are correct:

• Her dinin farklı kuralları var.
• Her dinin farklı kuralları vardır.

The first sounds more natural in everyday speech.

Yes, you could say:

Her din farklı kurallara sahiptir.

This is correct, but it sounds more formal and less everyday than ... var.

Compare:

• Her dinin farklı kuralları var. = natural, common
• Her din farklı kurallara sahiptir. = formal, written, academic

So learners should recognize both, but var is extremely common and important.

The neutral structure is:

• Her dinin = possessor phrase
• farklı kuralları = noun phrase
• var = predicate

So the sentence is:

[Her dinin] [farklı kuralları] [var].

Turkish often places the main predicate at the end, so var naturally comes last.

This sentence is a good example of a common Turkish pattern:

Possessor + possessed noun + var

Because of vowel harmony, which is a basic feature of Turkish.

• din has the vowel i, so the genitive becomes -in → dinin
• kural has back vowels, so the plural is -lar
• then the 3rd person possessive is -ı → kuralları

So the forms are shaped by the vowels in the word.

You do not need to memorize this sentence as random pieces; the endings follow regular Turkish sound patterns.