I been using compusa dvdr they're 4x but after burning at 4x the data on dvd can't read but if I burn with 2.4x it'll work, why?

Which burning program are you using? You may need to enable buffer under run protection.

Generally speaking if you burn at a lower speed it's more likely the data you will write will be accurate, always enable disk verification to make sure the data you have written is correct.

I have a 20x DVD-RW but I always burn at 8x for backups with verification enabled.

Also, bubblebobble, ace, what an addictive game

Store-brand media are cheaper...
because there are not as many "quality control checks"-- there can be coating flaws.
What Leb suggests is a good idea for important stuff-- anyway.