Do Mushroom/Jungle Biomes spread?

[Boltlord]

I want the Truffle to move in, but I am too lazy to make artificial one, so I will basically place mushroom grass seeds on the surface jungle
Will the Mushroom Biome spread and take over my whole Jungle?
Will the Jungle spread into the Biome, destroying it?

Also what happens to the Truffle if his house and his area (Mushroom Biome) would be clentaminated with Green Solution?

 

[LoveSpreader]

Will the Mushroom Biome spread and take over my whole Jungle?

Will the Jungle spread into the Biome, destroying it?

Neither biome spread. The biomes apart from the three spreading biomes do not convert any existing block(grass block for example) to a different block. However, they do grow if there is space of their medium of choice. If you plant a jungle/mushroom seed on mud, the biome will grow as long as there's mud, but they won't consume the other.

Also what happens to the Truffle if his house and his area (Mushroom Biome) would be clentaminated with Green Solution?

Haven't tried it, but he shouldn't leave immediately. If he dies, he just won't respawn until there's another house in a valid mushroom biome.

 

[Aurora3500]

I want the Truffle to move in, but I am too lazy to make artificial one, so I will basically place mushroom grass seeds on the surface jungle
Will the Mushroom Biome spread and take over my whole Jungle?
Will the Jungle spread into the Biome, destroying it?

Also what happens to the Truffle if his house and his area (Mushroom Biome) would be clentaminated with Green Solution?

Unfortunately, it is required to make an artificial Surface Mushroom biome in order to get the Truffle to move in. The easiest way to do this is to make a mud platform high in the air so it doesn't interfere directly with your world's surface and have 200+ blocks of mud on a long platform, and put Mushroom Grass Seeds on them. I frequently do this by nature in my worlds and is great for easy access to mushrooms in my opinion.

The alternative is to get clentaminator and make a section of your surface jungle into mushroom instead, though this will still have the risk of Corruption eventually getting to it, unless there is hallow surrounding you jungle.

For how it spreads, what Freenight said applies to that which they explained. Same with what happens if the Mushroom biome is clentaminated.

 

[Dragonlord]

To expand on Aurora3500's suggestion about a mud platform in the air, a good way to do that is replace a floating sky island's dirt with mud, and then turn the island into a mushroom biome, so it is out of the way without being too much out of the way.