There is certainly some delay in milestones, which may be a normal variation.
However, this does require a detailed developmental assessment. You should be referred to a pediatrician/ developmental pediatrician for assessing the extent and the possible cause of this delay.
It could be something as trivial as low Vit D, or it may be treatable condition like Hypothyroidism, or some other reason.
As I said before, this could be a normal variation, but I would be comfortable only after getting a clean chit from your pediatrician,
Dr Gupta, MD, Pediatrician, Member AAP.
The ubiquitous "Google Doctor" :)
I wish diagnosing conditions was as easy as Googling it, but hypothyroidism can be difficult to diagnose in mild cases.
Of course, I am not suggesting that your kid has hypothyroid, just used it as an example.
Yes, you can certainly give MV with Vit D.
Do remember to leave a positive feedback so that I am compensated for my time,
Hope to hear from you again after the opinion of the doctor,