According to the Minecraft Wiki
Trees grow normally, and their leaves take a dead-looking brownish
color like in desert biomes.
So trees can be grown as normal (as long as you are careful about making sure that lava doesn't just burn them all down), however
There is no way to place water in the Nether in a Survival game
Placing water source blocks with the bucket causes the water to instantly evaporate (with a hissing sound). You can still grow wheat in the Nether, however it will grow very slowly without water (also see the Wheat page on the wiki).
This also makes growing sugar cane impossible, however I believe that growing Pumpkin and Melon is largely unaffected by this as water only affects the rate at which the stem grows (which can be sped up with bonemeal), not the rate at which the Melon and Pumpkin themselves spawn. (The wiki does mention that Pumpkin cannot be grown in The End, but doesn't mention the Nether. I believe that Melon should grown there successfully but I haven't verified this).
Finally
Overworld mobs like pigs and zombies do not randomly spawn in the Nether, but throwing chicken eggs and constructing golems works as normal
So you will be unable to breed cows or pigs for food without using mods, however you can breed chickens by throwing eggs.
Its also worth mentioning that Nether Wart only spawns in the Nether, but can be grown in the overworld if you take a block of Soul sand with you.
Sadly, no. The Hatch block is an interface to an internal machine state that is incompatible with Managers. A Manager must have an inventory in the vanilla Minecraft sense: a storage space that can both have things added and removed. A Forestry GUI slot (and Buildcraft GUI slots in general) are implemented in such a way that they're merely visual interfaces to a non-inventory (in the Minecraft sense) storage space.
One way you can see the difference is that you cannot use BC wooden pipes to pump items out of an input Multifarm Hatch. If it were merely a block interface to the top-right Multifarm inventory slots, then pumping the input items (seeds, saplings, etc.) out through the input Hatch would be possible. Since you can't do that, a Hatch doesn't connect to a proper inventory. Without a proper inventory, a Manager doesn't have anything it understands as manageable.
Source: tooling around in Creative mode.
In theory, one way to "manage" a Multifarm in a RedPower2 pneumatic tube system would be with a Transposer/Filter/Retriever and exploiting the pneumatic tube "clogged" mechanic to automatically prevent the machine from drawing more items from the connected supply inventories when the farm and connecting tubes are full. However, experiments shows that in practice this doesn't work.
Although Farm Hatches are "clever enough to know which item goes where" according to the Forest Wiki, it also says:
Note: Tubes
RedPower 2 Tubes behave differently from Buildcraft Pipes! This is not a bug.
Through testing, this "different" behaviour is that Farm Hatches are not smart when connected to pneumatic tubes, as everything is dumped into the "soil" slot. With such a large hat put on this "difference" as being "not a bug" in the wiki, I can't help but conclude that this behaviour is intentional. The effect is that Multifarms are mostly incompatible with RedPower2. Consequently, an RP2 system appears to be able to supply humus and other "soils", but not fertilizer or "germlings".
If just maintaining a full soil inventory is enough, then a Retriever makes the most straightforward setup:
This keeps one stack of soil in the Retriever's inventory, which it will automatically eject toward the Farm Hatch as soon as there is any room in the Multifarm's soil slots. The rest of the stack that doesn't fit will "bounce" off the farm, backing up the Retriever and "clogging" it. When clogged, the Retriever refuses to retrieve any more items, preventing the tubes from being full of bouncers. A slow tick (15s in that shot) means that not too many stacks are pulled in the interval between the farm being filled and the clogging backing up the tube system. Any stacks that were pulled in that window bounce off the "full" Retriever. Normally they would continue bouncing back and forth, but adding the extra return tubes lets them go back into the stocking barrels.
As a result, when the farm runs low it refills from the pipe behind the Retriever, the Retriever pulls more to bring its internal inventory back up to a full stack, and any extra stacks pulled (the number is a function of the tick length) bounce around for a bit until they find their way back to the barrels. During normal operation the tubes contain no bouncers for the majority of the time.
Best Answer
ilmango is a very good youtuber that helps explain the mechanics, from chunk loading behaviours, tick mechanics, and spawning mechanics. He has posted a video about how phantom spawning works, and a demonstration about how farming them works
Additionally, it was Mr. Tiger that came up with the original farm that uses these mechanics, to drown the phantoms. Here is the tutorial for the farm: