To my foreign ear, Russians speaking at normal conversational speeds will pronounce вкусная and вкусное as something very close to:

вкуснəй

That is, with the vowel after the н (а or о) completely reduced to a "schwa", and the final vowel (я or е) reduced so much that it is hardly even a distinct syllable -- it's closer to "diphthongal" y in English "boy" or й in Russian мой. So, in essence, the word seems to have two syllables, not three.

However, when Russians are speaking more slowly and carefully, you can hear the three syllables, but both words still sound the same (FKOOS-nə-yə).

On the other hand, IMHO, the first я and the е in пятьдесят ("fifty") are both reduced to и, NOT to ə (schwa). Only the final я, being stressed, is unreduced.

P.S. I agree with it-ogo's advice that it's perfectly okay for you, as a foreign learner, to pronounce words more carefully than native Russian speakers do. Similarly, if you're a foreigner learning English, it's perfectly okay to fully pronounce the "L" in walk and talk, even though the "L" in these words is totally silent in the normal speech of many native speakers. (Thus the joke, "Have you seen the new Chinese cookbook? It's called 101 Ways to Wok Your Dog.") And other native speakers basically reduce to "L" to something like a "W", which alters the quality of the vowel "A" before it, and turns it into a diphthong. And still other native speakers pronounce the "L" as a normal "L".