Betta Fish: Update on my rescued Betta

For context: This is my previous post on a betta which I found accidentally. I've made a post on reddit regarding it – link

Thanks all for your recommendations and suggestions. Sorry I couldn't reply to the comments.
Now for the update part, I couldn't get a 5 gallon tank for the betta due to the space constraints where I live and I couldn't afford it too for the time being. I went for a 3 gallon tank . Added river sand some fox tail , sponge filter and a couple of hinding spots and the fish is in cycle now. I'm in a tropical country so heater won't be required

I know this may enrange the enthusiasts here and I might be accused of not providing it a minimum of 5g, but this is the situation right now (and on my side I did not choose the fish on choice ) but I want to give it a better life as much as possible. So please provide any suggestions to improve my current setup , also would like to know if my fish is in good condition . I see a tiny white spot in the tail but chat gpt says it's ok .