Answer:
A trail, a union, together tied. Come across me and you will find you cannot change the course I'm on. Without me you cannot travel on. What am I?
I tell people to be careful when handling boxes.
Curtail me thrice I am a youth; behead me once a snake; complete I'm often used in truth when certain steps you'd take.
The dirtier I get, the whiter I am. What am I?
What kind of table can you eat?
Special abilities and brightly colored underwear are all you need to be one of these.