Methylcobalamin vs cyanocobalamin

My homocysteine is on the high side. I am at risk of heart attack. For this, my doctor prescribed methylcobalamin and folic acid.

I got curious this evening when I saw the cheap vitamin B - complex sold in supermarkets. Cyanocobalamin - vitamin B12. So what is the difference between cyanocobalamin and methycobalamin? Aren't they both vitamin B12? Hey, what is the prefix cyano mean? Scarry...

I found out that not all vitamins are created equal. cyanocobalamin-versus-methylcobalamin?blog=27 Cyanocobalamin vs methylcobalamin.

What about calcitriol vs vitamin d?