Punch tumble Weed to obtain stick, bones and clay. 
New ages will be unlocked as you progress.
You will be in adventure mode until you unlock the Smelting Age. 
You can dig below bedrock to get to the Neather once you have a bedrock pickaxe.
There are dimensions underneath the Overworld and Neather.
Skill books unlock new mods when you right click with one in your hand.
There is a town building mod installed.
Journey map is locked until the Modern Age.
ME Systems will be unlocked during the space age.
You can find Draconium in Dungeon chests.