Her varyasyon, test sonuçlarına dayanarak değerlendirilir.

In Turkish, her (“every”) always takes a singular noun. You cannot say her varyasyonlar; you must use the singular form her varyasyon.

test sonuçlarına is an adverbial phrase in the dative case. It literally means “to/onto the test results” but here it’s used with the participle dayanarak (“relying on/based on”) to mean “based on test results.”

Let’s break it down:
1) sonuç = “result”
2) -lar (plural) → sonuçlar = “results”
3) -ı (3rd-person possessive) → sonuçları = “its/the results” (marking them as definite)
4) -na (dative) → sonuçlarına = “to the results”

The possessive -ı is needed because dayanmak (“to rely on”) normally takes a definite noun in the dative.

That n is a buffer consonant used when attaching a vowel-initial suffix (–a/–e or –ı/–i) onto a stem that already ends in a vowel. Here, the possessive -ı ends in a vowel, so we insert an n before adding the dative -a → -ına.

dayanarak is the adverbial participle (–arak/–erek) of dayanmak (“to rely on, to base on”). It literally means “relying on,” so placing test sonuçlarına dayanarak before a verb means “based on test results…”

Yes. -dayalı is an adjective-forming suffix meaning “based on.” You can say:
Test sonuçlarına dayalı olarak her varyasyon değerlendirilir.
Both mean “Every variation is evaluated based on test results,” though dayanarak is more directly verb-based and common in technical writing.

değerlendirilir is the passive present-simple (“is evaluated”). In formal and technical Turkish, passive is often used to focus on the process rather than who performs it. If you wanted an active form, you’d need an explicit subject (e.g. “Biz her varyasyonu… değerlendiriliriz” – but that’s unidiomatic).