You start the game on Tier 0. Building a Tech Center (available in the outpost) unlocks Tech 0 units and morphing it takes you to Tier 1 (T1, for short), unlocking T1 technology
A T2 tech center is required to morph the outpost to T2 or morph basic factories into advanced factories
A T2 outpost can build T2 factories and structures, including a T2 outpost directly
If all upgraded Tech Centers (nothing prevents you from building many) are destroyed, that locks out some of the advanced units from the advanced factories and outposts, but not all of them