Should I write a comma in the next examples?

1) Hello friend,

[text of a letter].
2) Hello, friend,

[the same].
I have noticed that many people don't use a comma. They just say, "Hello someone, ". Is it right?

And one more question. Should I use commas after and before "please"?

1a) Can you, please, help me?
1b) Can you please help me?

2a) Can you help me, please?
2b) Can you help me please?

3a) Please, help me.
3b) Please help me.

Which sentences are correct?

I'm sorry if you have been over this before but I was searching and didn't find the answer.
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Comments  (Page 2) 
Yes, Pieanne, my emoticons are doing well because I simply decided to use Explorer if needed. Emotion: smile
"Hello, all of you" ?

"Hi everyone"?

You mean these phrases are appropriate, don't you?
A wise decision, Ruslana!

Yes, they're OK, but very informal.
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I know I am a very wise person! Emotion: big smile

Thanks for your help, Pieanne and YoHf.
It's nothing! (I like you little smiling rainbow!)
You're welcome!

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Pieanne, I like you like it!

By the way, It's nothing! = You're welcome, right?
Yes. There's a thread about it in the recent "vocabulary & idioms" section, you'll see. "you're welcome" has a synonym?

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When addressing directly someone, place a comma before their name. There is no exception.
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