how do you play defensively though ?

Well what i've understood over the years of playing is that defensive play is exactly what it sounds like. Instead of being an aggressor in the position you play passively and reactionary watching what ur opponent is doing analysing their ideas in an effort to breaking down their attack. Yes it is somewhat hypermodern play however that type of play is more like allowing ur opponent to take the initiative and then attempting to chip away at their structure, which is in large part positional play. 

Also based on the questions ur asking you seem to be trying to put the ideas of chess into a defined box. Like what is defensive play what is tactical play what is positional play. I feel as if any move a person makes on the chess board should have elements of all three of these aspects of play in them. So do not separate these ideas in your mind but instead try to incorporate them into everything you do on the chess board in the right ratios. 

A solid defensive opening is probably to march all pawns 1 space?(I've seen a really a high rated opponent use it with much success)

So,Does it mean to extend your pieces,or to cautiously wait until your opponent has created a territory in which he cannot sustain?

Defensive play to me is protecting my pawns and pieces from attack and capture. This is good except sometimes I spend more time doing this than planing my own tactics and plan of attack. This usually means my opponent has me on the run.