One is the Furniture Mod which requires Minecraft Forge version 1.8.
The other is the Still Hungry Mod which requires Minecraft Forge version 1.7.
You can't, 1.8 is a major update. You have to find mods with same major versions.
E.g.: 1.8 - 1.7 Not good
1.8 - 1.8.2 good
That is not possible. You can try to find Furniture mod for 1.7.
No. You need the same version of forge of the mod so you can play them or maybe if you have another computer you can name your computer the version name!
The Minecraft Forge version you're using needs to be the same version as the mods you use. For instance, if using Minecraft forge 1.14.4 both of mods used need to also be version 1.14.4.