What these sentences's difference is? "as long as" and "so long as"
1) You can buy alcohol as long as you're over 18.
2) You can buy alcohol so long as you're over 18.

Question

Answer

Neal has a good answer.  Here's some examples:
"You can stay as long as you like"  (can't use "so")

The rest mean the same thing.
"So long as I'm the boss, it will be done this way"
"As long as I'm the boss, it will be done this way"

"We can watch TV so long as you don't wake the baby"
"We can watch TV as long as you don't wake the baby"

Answer

Hi Talcha

Both are good.  In this context (conditional phrase) they mean the same and you could use either.

In UK English, the only time that it would not be grammatically correct to use 'so long as' is when you are referring to time, such as in the phrases "as long as you like" or "as long as you live".

Neal