Which of the following is formed after dedifferentiation?

In flowering plants,senescence is an active developmental cellular process,which suggests growth and function. This is best exemplified by:

Living differentiated cells, that by now have lost the capacity to divide, can regain the capacity of division under certain conditions. This phenomenon is termed as $.........$.

The living differentiated cells,which regain the capacity of division under certain conditions,are called ....

In tissue culture experiments, leaf mesophyll cells are put in a culture medium to form callus. This phenomenon may be called as

In a developing embryo,analyse the consequences if cell divisions are not followed by cell differentiation.