Boundary condition to single direction in the subspace of Mixed function space

[dokken]

@kumar

left_corner_vertex = mesh.locate_entities_boundary(msh,0,left_corner)
dofs = fem.locate_dofs_topological((ME.sub(0),ME0),0,left_corner_vertex)
bc_left_corner = fem.dirichletbc(bottom_value1,dofs,ME0)

You are taking the first sub-space of the mixed element, which is V, not V.sub(0)

@kumar

ME = functionspace(msh, ufl.MixedElement([V, P1, P1, P1, P1]))

You can check this by printing ME.element.num_sub_elements, which gives you 5, not 6.
Thus, you would have to change:

@kumar

right_dof = fem.locate_dofs_topological ((ME.sub(0),ME0.sub(1)),0,right_corner_vertex) #Having doubt regarding the bc on right corner 
#to constrain displacment only along y direction.
bc_right_corner = fem.dirichletbc(bottom_value2, right_dof, ME.sub(0))

To

ME0y, _ = ME.sub(0).sub(1).collapse()
bottom_value2 = fem.Function(ME0y)
bottom_value2.x.array[:]= 0
right_corner_vertex = mesh.locate_entities_boundary(msh,0,right_corner)
right_dof = fem.locate_dofs_topological ((ME.sub(0).sub(1),ME0y),0,right_corner_vertex)
bc_right_corner = fem.dirichletbc(bottom_value2, right_dof, ME.sub(0).sub(1))