Right click on grass will spawn some flowers and tall grass. Right click on wheat, pumpkin or melon stem, will grow it to maturity. If the growing requirements are met (check the MC wiki) right clicking on a sapling will grow a tree.
No
Use bone meal.
I think you can use bone meal on grassblock to get it but not sure try it.
No
You can't you can only craft bones to bone meal, unfortunately not the other way round :/ Sorry
Right click on it using bone meal. To get bone meal, you need to obtain a bone and then put it in your crafting table.
you get bones and put that bone in one crafting spot to get bonemeal (im a minecraft player since alpha)
If you have worldedit select the area you want trees in and do //forest
make bone meal
You use it to dye wool, and also combine it with Bone Meal to make paler dyes. In 1.3, you will be able to make writable books using it.
Currently the only use for ink sacs on Minecraft is for dying wool. Using a raw ink sac on wool turns the wool into black wool. Using the ink sac with one bone meal creates gray dye and using it with two bone meal makes light gray dye.
You can craft bone meal. Bone meal is especially useful for farming and dyes (for wool). You will get 3 bone meal from 1 bone, and if you wish to use them for farming, when you right click on a growing crop (i.e. wheat, pumpkin stem, melon stem, carrots, potatoes), the crop will fully grow. Note, for a pumpkin or melon, only the stem grows. However, it saves the time of waiting for the stem to grow. You can also use it to dye other dyes lighter. For example, put rose red dye in the crafting table with bone meal and you make pink. In the related links below is the wiki article for more crafting and what you can do with bone meal.