The gist of Yoon is that it takes a character from the い / i-sound column
For example; き , ひ , り / ki , hi , ri
Followed by a smaller version of one of the y-sound row characters
Y-sound row: や , ゆ , よ / ya , yu , yo (small variant: や → ゃ , ゆ → ゅ , よ → ょ)
(you will only see the small versions of these in Yoon application, never any other context)
In doing so, it condenses this from two syllables into one singular one
Using the example you provided of kya;
If you saw きや , each character would be a syllabul - like “ki-ya”
However using Yoon mechanics, if the や is small like ゃ - the i in ki would be removed
きゃ would read as “kya”
If you know that pattern, that’s all there is to Yoon
ひよ / hiyo
ひょ / hyo
りゆ / riyu
りゅ / ryu
It’s a little tricky at first since the size difference is a little subtle, but once you get an eye for it it clicks fast. You’ll get there officially eventually so don’t worry about it quite yet, and it shouldn’t be too much a headache when you get there either.
Yup, if you get that checklist under your belt, you’ll have learned all of Hiragana and it’s mechanics. Take some time to get comfy with it, sure, but once you are feeling confident and ready- then move on to Katakana. As you practice literally anything with Japanese, you’ll inevitably get more experience with it all so you don’t have to be 100% perfect right at the start. Best way to sharpen up your skill is to start applying it
I think biting too much off at once could tangle you up in the moment, so keep working on nailing down Hira/Kata first and don’t worry too much of this front quite yet- but when you’re feeling more prepared;
Pretty much any basic / all-encompassing language learning program will get you a good start on some basic vocab (and usually without any Kanji for a while). Duolingo, Busuu, Genki Textbooks all get you a nice little supply and ease you in very smoothly. I like these options since it will give you some context in how they are used in sentences, too.
Bunpro also has a pretty great vocab section attached to it, and something like Anki can definitely get you a huge quantity- but they’re not as “step-1 beginner” designed as the previously mentioned.
By the time you start seriously looking into bringing Kanji into your workflow, here at WaniKani (if you decide to use it) will introduce you to thousands, too.