Responses in bold! Copied your whole message so I could keep track of all the questions:
-Pokecommunity didn't complete all new Gen V icons, so I found a link for you:
https://drive.google.com/drive/mobile/folders/1xxOEbLr1mD-RDqWS9g1t7bOas-QeUrGE?usp=drive_open
Thanks!
-I guess your Emerald hack will have 85-90% of pokemon that have second frame sprites in the first release version, right? and is it hard for you to create some custom second frame sprites for some pokemon that don't have it yet?
Not quite that many sadly, closer to 50%: every Pokemon from gen I-IV and most of V have second frames, but the rest are all single frame animations. I can make second frames but it's very time consuming, so I haven't made any custom ones yet (that'll be a version 2+ thing I think)
-I prefer the design of Pokemon & stats menu to stay originally as it is instead of HGSS and/or BW styles (like in Radical Red, Theta Emerald Renev & maybe Unbound), and for pokedex, well maybe a new PokedexPlus from this site but with Emerald design, but it's up to you.
I'll be keeping most of the Pokemon menus close to their original design. At some point they'll need to be modified a bit to support longer move/Pokemon/ability names, but I'll try to keep the general look. I'll be using The Xaman's Pokedex though, it's like having all the hack's documents in game!
-Are May & Brendan's pokemon teams different (aside from starters)?
Yeah, they got completely different teams aside from their starter and Swellow; there wasn't much to work with there lol.
-Does it have a rival battle inside the Pokemon League before battling the E4? (Like Barry/Sinnoh rival battle in the Pokemon League (DPPt))
I had that in my old 2012 version of Emerald, still deciding if I want to have it in this one too! There's a daily rematch with them in the post game at least.
-Does Scott from Battle Frontier have some battles in this hack to demonstrate players?
No, but I'll be adding battles with the Frontier Brains in the main game as a way to get certain items.
-I know it's obvious, but I want to say that I'm sure that in this hack, trainers in the Victory Road have mega evolutions like in EXWY, RRSS, & PSPM.
Yep! Some Ace Trainers even have them a little earlier this time.
-Does this game have Medal challenges like in B2W2, or maybe a challenge like this in Pokenav?
Nothing like that yet, maybe in future versions.
-Will there be some mirage spots/places like in ORAS, maybe with some legendary encounters?
No mirage spots, but most Legendary Pokemon have new locations added just for them.
-Will there be some Item/Money sidequests like in Alola games?
Yeah, I'm still working on those - there's an "interesting" one to get the Gyaradosite involving a lot of Magikarp.
-Does Safari Zone have 6 areas before E4/Post-game, or still 4 areas?
All six areas are available before post game.
-I hope we can revive prehistoric pokemon by giving fossil items, instead of catching them as wild pokemon (Theta Emerald Renev).
Yep! The fossil guy can revive all the fossils, and you can get as many of each as you want (though they're pretty rare after the guaranteed ones).
-I wonder if you can add some new trick house puzzles.
I hadn't actually considered that, it's a good idea. Could add a few more in the post game.
-Is Soothe Bell available earlier in the game so we can evolve Pokemon that requires friendship easier, and because to evolve it, it takes a long time in Gen 2 & 3, longer than the next generations.
Yep, it's available somewhere around Petalburg Woods, along with a Friend Ball, which instantly grants caught Pokemon enough friendship to evolve.
-What was your hardest part when your were working on your Emerald hack, and what will be the hardest part when you'll be working for some next versions?
So far it's been the code for Rotom's form change; it turned out to be a lot more involved than I thought, so it took a couple of tries to get it right! I want to add inverse and 6v6 modes to all the Frontier facilities, so I think that'll be the hardest thing to do in later versions.
-Before the release of ORAS, fans were listening to RSE soundtrack with some excitements, this year (or these days), I'm doing it the same but for your Emerald hack, listening to some Hoenn songs before playing the first version, or the version with Gen 8 Pokemon. (Crazy, I know ^_^)
Haha, I have the RSE soundtrack on as background noise while working on the hack sometimes. Helps to get in the mood!
-Are you working on your hack too much, or are you working on it sometimes and have some important and free moments like work, other hobbies, family & friends, going out...etc ?
Probably working on it too much, but I make time for all those other things too so I don't burn out. Got a 4 week holiday coming up so that'll be a lot of hacking time!
There's a very good chance gen 8 mons will be ready to go before I have a first release ready, so I might just delay the hack a bit to have them in version one. Will see how much I get done this week.