BDS vs ODS Column

I usually found it difficult to distinguish between ods c-18 and bds c-18
columns. Both involve octadecasilane chain.

Finally I came to know that ods contains free -OH functional group while bds i.e. base deactivated silica column has -OH groups deactivated or blocked. This is the reason why bds columns are also called as endcap columns.

The questions arise now:

1. We have base deactivated c-8 columns.
Do we have base active c-8 columns?

2. If not then why?

3. Can we use bds c-18 in place of ods c-18 column?

4. What happens if we do so?