Help with 1.16.5 Forge imports

[ShipHeatRook]

Hello! I've been updating old and abandoned mods to the newer versions of Forge as an hobby and to learn more and more of coding myself. I've happened to run into an outdated mod that, in 1.12.2 Forge, implements a new fluid: however, it does so by calling
 

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net.minecraftforge.fluids.Fluid

and
 

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net.minecraftforge.fluids.FluidRegistry

which apparently isn't possible for 1.16.5 Forge. I need the first one to initialize the fluid and the latter to add it to the registry and use it elsewhere in the mod, so how would I do it?
Also, is there anywhere I can follow Forge's updates and changes in its classes or structures? It's not the first time I've run into a problem of this sort. Sorry if my question sounds dumb.

Thanks so much!