New beginner with a lot of questions! Any advice would be appreciated! :)

Hello. If you're reading this, thank you so much. However, I have a lot to say and if you don't have the patience to read it, you might as well do yourself a favor and leave. <3

Okay so anyways a little background about my tank and myself -

I'm a new fishkeeper as of 4/9/21. I've always loved fish and aquariums. I love the way the move, act, swim and everything. My sister says I was a fish in my past life but who cares. If you wanted to define the lowest of the lowest of fishkeeping as far as experience, that's me! So yeah. I have a lot of questions, so please keep reading!

Basic Information -
Gallon Size - 10 gal.
Heater - Yes, 50W.
# of Fish - 2
Species - 1 Platy (FEMALE) 1 Molly (MALE)
Substrate - White gravel about 2 inches as far as level.
Filter - Of course. I'm not as dumb as I used to be.
Aerator - New installment as of yesterday. (I'll get to that later.)
Plants - 2 and artificial (plastic.)
Decorations - One FAT log with holes large enough for fish to hide in. (Also artificial and plastic.) & A tiny cute blue cave that I'm using to hold my air stone down.
Cycled - I'll get to that later.

Alright, SO! My aunt helped me set up my new aquarium. She has had fish since 2019. A Platy actually that she has managed to keep alive and healthy since 2019. Furthermore, she also has a 20 gallon decently kept tank. Like I was saying, she helped me set up my tank with all of the necessary fixings. We used my tap water to fill up my 10 gal. and we added stress coat once full. She told me to let the tank sit for 48 hours before we get the fish and I did. (Keep in mind that the things she told me to do are the same things she did with her fish. However it took her 3 days for her 20 gal. water samples to be good for her to get fish.) Furthermore, she came back to my house on 4/11/21 (2 days later.) So her and I ran to pet smart with my topfin water sample and it was tested good for fish. Keep in mind that I literally got a nod and smile when we asked the worker if my water was good. So like any fishkeeper I was super excited and I picked my fish. I ended up getting 1 Molly, 2 Platies, and 1 Guppie. I got home and let the fish acclimate in the water bag for 15 mins. After that I scooped them into my tank and watched my new fish. Over the course of the next 6 hours, I noticed that my fish would hide behind my plant A LOT. I researched and believed that it was normal. In addition, my Guppie was spending A LOT of time around the surface; gulping air. Long story short, I went to bed and by the next day, My 1 Guppie and 1 Platy had died. Literally. I was shocked and scooped them out immediately. My Molly and other orange platy were still acting normal. About 3 hours later, I noticed that my Platy and Molly would constantly swim up to the surface and gulp air. They would then sink like they had no control of their bodies. As a result BOTH of them ended up dying 1 hour later. After all of that I researched like crazy for the entire day and learnt quite a lot that I would have never known without that experience. The next day, I took a water sample and brought it back to my fish store. I told her my story and she said that it was a problem with oxygen and convinced my mother and I to purchase an air stone. I thought it was swim bladder but hey, what do I know? So my mom and I got 1 Platy and 1 Black Molly plus an airstone. I went home and installed the air stone while the fish were acclimating. So I ended up adding them and they've been fine since 4/12/21. I also fed them dried bloodworms(pinch) on 4/13/21 and they BOTH ate.

QUESTIONS & CONCERNS

#1 - Ever since I fed my Platy, she would go under the log and shimmer. Like she's nodding "no." Her fins would also be clamped as well. Keep in mind that my Platy would also swim around the tank with NORMAL swimming patterns. However, she went to different layers of the tank and would also do the shimmering. Is this normal? If yes, why. If not, what can I do and what is wrong? Also the temperature for my tank for these last days has been 74-78 degrees F.
#2 - Now, this morning, I woke up and both of my fish were in the comfy log so I assumed that they were sleeping and did not want to be disturbed. So I left them alone for about 4 hours before taking action. (Keep in mind that I woke up THIS MORNING.) Furthermore, I started to get worried and lifted up the log with clean hands. (no soap.) The Molly immediately swam out. (My Platy was already out.) However 10 mins later, she swims right back into the abyss of the log.
#3 So I leave her alone. My Molly is female; same with the platy. While my Molly was hiding my Platy was mostly normal and would swim around and shimmer. Swim around and shimmer. The temp was 74 degrees last time I checked which is normal for tropical fish. Now, is this normal? I also noticed that my Platy would go into the log and shimmer as well. Keep in mind that I did NOT feed them today.

Lastly before you say disease, I checked the appearance of the fish 24/7 ever since I got them. I haven't noticed any sign of Ich, Velvet, parasites, or any disease. Their behavior is mostly normal and they are NOT gulping for air. However, my Platy & Molly would RARELY. Key word = RARELY go to the surface and gulp 1 bubble before normally coming down.

#4 How do I know if my tank is cycled? I mean I tested this water twice and got a "good" result at the fish store. I don't trust it but I also don't have a kit which I plan on getting soon. IN addition, I also noticed my water to kind of misty/milky at the top. Is that a good sign? I heard that it was bacteria.

#5 Are my fish lonely? Do I need to add 1 more female molly and 1 more female platy?
#6 ALSO, do I need to feed my fish a variety of foods? My aunt only feeds them bloodworms and her fish have been very healthy. Can I do the same?

Thanks and any advice would be MUCHHH appreciated!

 

Okay!
Also, can someone please explain to me what products I need for a fishless cycle, and do I need Quick Start or not?

• You need an ammonia source. Some people use straight ammonia, but you have to be careful to not get one with additives. Others use fish food, or a piece of fresh or frozen shrimp from the grocery store. You also need a test kit so you can monitor the growth of the bacteria colony.
• Some people have reported accelerated cycles using bottled bacteria, but many have said it doesn't help. I don't think I'd bother.

 

Okay!
Also, can someone please explain to me what products I need for a fishless cycle, and do I need Quick Start or not?

I agree with the above. Most importantly you need an ammonia source. You can buy liquid ammonia, but what I always do is cut up a tea bag, wrap a bunch of fish flakes in it and place it on the filter intake. The ammonia produced will go straight into the filter.
Secondly, bacteria in a bottle does work from my experience (I used API quick start on my first tank and it cycled in a week), however, old filter media is much more effective. If you can squeeze a disgusting old piece of media into your tank (make 1000% sure there are no diseases where it's from), your cycle could be done in under 2 weeks honestly (still test your water, don't just assume time has passed and your all good).

With returning the fish, I'd just use a sandwich bag, but call the pet store first and ask if you can return them. They should let you, if they don't, explain you were told the wrong information. Then they pretty much have to let you. I know it's difficult returning or rehoming fish once you've built a connection to them, trust me, I've experienced it too, but thank you for putting their needs and wellbeing first. A lot of fishkeepers won't. You're doing good. Please don't let this discourage you.