I have had 3 grade 2-3 concussions I have a brain cyst inlarged ventroles in brain and large groupings of blood vesicles in brain can I play rugby.

Not advisable. Concussions which represent brain damaging events, are cumulative in effect. It appears you already have visible damage on imagine. Continuing to play a vigorous contact sport with the likelihood of further concussion and brain injury would be very dangerous and I'll advised.