Got the blackberry in 2018 and it was a 1 or 2 year old bush, possibly two bushes in a 5 gallon pot and named 'babycakes' blackberry, a kind of hybrid.
They are one of the few productive plants that grow well in semi-shaded or damp conditions which makes them ideal for those unproductive corners of a garden where other plants struggle. As long as the soil is reasonably good quality and not alkaline they will usually do well. -Growveg
Our red currant was 10" tall in 2018 when we got it.
How to Grow Berries in Containers
Currants
heirloomgardener
Simple Layering. Simple layering can be accomplished by bending a low growing, flexible stem to the ground. Cover part of it with soil, leaving the remaining 6 to 12 inches above the soil. Bend the tip into a vertical position and stake in place (Figure 1).
ces.ncsu.edu Berries seeds