[OSM-dev] How to render zoom levels 0 to 11?

Hi List,
as i see it on the dev server there are no tails for zoom levels 0 to 11
on it.
Is it possible for me to upload such tiles, and, if yes, how should i
render them for a specific area?
As i saw it on bandnet zoom level 10 e.g. was a concatenation of 4 tiles
of zoom level 11, and so on, am i right?

Greetings,

Damian