Are you able to use music from video games in flash games and give credit to the game/company or will you get into trouble for it?

Hes absolutely right. Its purgery and fraud. Thats like call of duty taking resident evil characters and selling it for ps4 and get 1 million dollars off of capcoms work

If you're not making any profit, then you should be good. If you are making profit from the game, then you cannot unless if you have permission to do so (well you technically could, but it would be illegal).