Should I confess sins that I have done when I was younger? I don’t remember everything, but I know I have sinned, but since i was unaware of it since I was younger, is it still sin? Also, is it OK to say I have lied, disobeyed parents, etc… rather than saying exactly what you did ?
If you didn’t know it was a sin, than you didn’t commit a mortal sin. But you may also confess venial sins. In Confession, you just give the type and number of sin - for example, murder, three times.
These may not be mortial if you can’t remember it, or are unsure.
You are more than free to confess these sins.
You only have to give enough info that the priest knows what he’s absolving you from. I.e. a word or phrase is fine.
If you decide to confess these sins from childhood, be sure to clarify that they were committed when you were younger, and not in the period since your last confession.