I saw earlier that other people filling their tanks with milk and potions(though they were on early versions) so I tried to do the same with a bucket of milk and a bottle of honey, but never working.

Is this bug, or actually removed feature in latest version?

Milk - removed in latest versions, if you know any mod that adds milk as placeable fluid, I can add compatibility by adding fluid effect for it
Potion - should work, I have to check it if it doesnt work

I just checked and potions do work. I thought honey bottle would work same as potion, but it was not.

I see. So milk should not be a thing.
But potions? Still don't work.
And speaking of potions, does bottle of honey count? Because it doesn't work either.

I'll check the potions, maybe I forgot about it. Honey is not a potion, so no honey is not supported to go into tanks, only potions with effects