Question

Disadvantage of Biconvex shape of RBC

Answer 1

disadvantage of biconvex RBC:
RBC carry haemoglobin at its centre that's why its shape is biconcave
Biconvex shaped RBC won't be able to do that

Answer 2

 The abnormally shaped blood cells can no longer flow properly through the veins and possibly cause issues with oxygen flow/absorption/distribution throughout the body.

The problem would be that, given that the cells would have the same volume, convex RBCs would have a lower surface area (spheres have the lowest surface area to volume ratio of any shape). The lower the surface area, the slower oxygen will dissolve in and out of the cell.