TI-API: API v2 migration documentation

Hi, I have an API 1.0 FAQ that states that I can refer to the API portal for documentation about upgrading to API 2.0 but I can't find anything on it.

Can someone point me to that documentation?

Does the pre-production endpoint still work?  Do I need to request access to API 2.0 if I already have access to 1.0?  Right now, I am getting 401 errors against the 2.0 endpoints after authenticating.

Thanks