Not sure I understand, but if you mean does it work in a 3 gallon aquarium, yes it absolutely would. My betta fish love these so much and lay on them. If you have a male, his fins will get heavy as he grows so it’s hard for him to stay near the top of the tank unless he has something to lay on. I put mine about an inch below the top of the water and he lays on it all the time (guessing you know that bettas like to gulp air from the surface of the water, unlike most fish).  Note though that in a 3 gallon tank you may have too much water movement from the filter at the top which bettas dislike, so you may need a bigger tank for your betta to really enjoy it and use it.

Any size would work. If you have any larger tank (greater than 5 gallon) I would get the large. If you have a smaller tank I would get the regular one. You should definitely have at least a 3 gallon or so though. Otherwise the ammonia will build up quickly and make your fish sick. Look into the nitrogen cycle online too if you haven't already!

I put it where my Beta hung out the most, yet he still chilled out in his favorite tree limbs instead lol... Just make sure it's not too close to the top. You don't want them to get stuck out of water.

Click on attributes/specifications on the website for the size you want and it tells you the length of the leaf hammock.

the leaf not super soft but not really ruff .My betta likes it

Female bettas don't have different opinions about decor than males. Anything a male would like a female would too

Po (my betta) did not like the hammock at first. I had to train him with pellets. I usually feed him 4 pellets a day. at least 2 of them I fed him on top of the leaf. Once he was on it, I guess the little guy just liked it. Now he sleeps on it here and there :). Plus its close to his heater and my room gets really cold so he loves sleeping on that leaf.