if replacing the heatblock and hotend in general on the i3 mini, what types can be used ?

Most anything along the lines of these. http://a.co/d/2qLJRJc

If you meant what I refer to as the heat break, you’ll see them for sale in the “Usually bought with this” suggestions.

Generally, anything that is MK8 will do (heat blocks, heat breaks, nozzles).