Hiccup and say ビール、ありますか。 ;)

Yea. I know you can drop the particle, but still. If the differences between the two 彼女がいない　　彼女はいない are as big as someone though that one has dissapeared and the other means don't have, it would be nice to get the difference between the situations they are used in down pact.

When you can drop the subject-marking particle, it is ALWAYS 「は」. You cannot drop 「が」.

I do not even know what 「ビールがありますか。」 means after having spoken Japanese for 5 decades as my native language.　

「ビールはない。」 = "There is no beer (to begin with).", "We don't serve beer.", "They don't serve beer."
「ビールがない。」 = "OMG the beer is gone! What happened?"

EXCEPTIONS: inside relative clauses and other sub clauses.
「ビールがないならコーラをください。」
「ビールがない国は少ない。」

Hi, I would like to know what is the difference between 「謝る必要はない。」 and 「謝る必要がない。」?

The thread is getting repetitive.

Former = Normal phrase. Can be used by itself.
Latter = Not a norml phrase. Use it as part of a longer sentence. Read my post just above.

Thanks, masaegu.

Can I say "謝る必要はない大丈夫です"　(I am fine so there is no need to apologize.)?

That is two sentences with no punctuation.

How about this "謝る必要はない、大丈夫です。"?

Correct grammar-wise.

The imbalance between the curt 「必要はない」 and the nicer 「大丈夫です」 needs amended. Hate to sound anal but native ears will rarely, if ever, miss these subtleties.