No, not at all. Apple is úll ("ool" with broad L); Iúil is pronounced like the English word Yule, with a slender L.
I did get the impression from the voice in Duolingo. I rechecked on Foclóir. None of the three dialects seem to have a "Yu" at the beginning. All are identical between úll and Iúil. With the latter half there are differences between the dialects, but I couldn't really notice a system behind it. Like the Connact "l" of Iúil sounds absolutely broad and totally homophone to Munster úll. Connacht úll on the other hand sounds like OO-le, something which I would expect of a slender l.
I guess I shouldn't dwell too much on it. I hope I get it in time. (although I have to say the dialect stuff IS interesting)
OTOH, I will probably never speak with anybody in Irish so the point is rather moot.
Actually, I stand corrected. I could have sworn that I heard the first letter pronounced somewhere, but you are right -- Forvo, Teanglann, and Wiktionary all give a pronunciation very similar to úll. Thank you for making me recheck my sources!
I heard the slender second i in Iúil so I went with úill (vocative and genitive of úll). Much good it did me.
For years i have pronounced this as Loo-ill. I have only now realised that it begins with a capital i and not an L.
An easy way to remember this month is by looking at the etymology of "July". It comes from Latin Iulius, named for the Roman emperor Julius Caesar after his death and deification. The letter J was originally just a modified I and was pronounced the same -- a tradition that's continued in most Germanic languages, and the J/I similarity is reflected here in Irish.
Can one say 'month of' as with some of the other months? And if not, what is the rule?