Definitely the same as. I don't think we ever use the same with. Well except for Person A: Oh no! I forgot to lock my house today. Person B. Same with Jenny. Which means, Jenny forgot to lock her...
Yes. It's a slang way of saying the same thing.
No. KB (kilobytes) is a measurement of data (1000B, 8000b) Mg (megagrams) is a measurement of weight, (1,000,000 grams)
Congruent.