In an elastic collision between two particles

A block of mass $\text{'}m\text{'}$ is hanging from a massless spring of spring constant $k.$ It is in equilibrium under the influence of gravitational force. Another particle of same mass$\text{'}m\text{'}$moving upwards with velocity, $u_0$ hits the block and sticks to it. For the subsequent motion, choose the incorrect statements:

Two masses, $2m$ and $m$ are connected by an inextensible light string. The string is passing over a light frictionless pulley. The mass $2m$ is resting on a surface and mass $m$ is hanging in the air as shown in the figure. A particle of mass, $m$ strikes the mass, $m$ from below in case $\left(i\right)$ with a velocity $v_0$ and in case $\left(ii\right)$ strikes mass $m$ with a velocity $v_0$ from top and sticks to it.