Are they same meaning? suit yourself / be my guest / knock yourself out

[Eureka]

Hi!

1. Suit yourself = be my guest = Knock yourself out

Theses expressions are interchaneable in meaning "do whatever you want". Whenever I watch T.V., to me, it feels like they are used in same contexts. If I'm wrong, could you please let me know how they are different in meaning or something else. And I'm also wondering which one is more casual among teenagers.

2. Why people say "you, too" not "me, too" when someone says "It was great
seeing you"?

As far as I know, "you,too" is a short response to say again what speakers said kindly like "have a nice day" "you,too" I thought I knew how to use "me, too" and "you, too" but now I am a little confused when I found such a response.

In this case, speakers just say how he feels from meeting someone like "It was great (for me)seeing you". So I think listeners also can say "me,too" which means "I am also happy to see you"

Can you help me understand that corretly?

Thaks a million in advance.
Have a good day!

[RonBee]

Hi!

1. Suit yourself = be my guest = Knock yourself out

Theses expressions are interchaneable in meaning "do whatever you want". Whenever I watch T.V., to me, it feels like they are used in same contexts. If I'm wrong, could you please let me know how they are different in meaning or something else. And I'm also wondering which one is more casual among teenagers.

They all mean the same thing.

[Charlie Bernstein]

1. Suit yourself = be my guest = Knock yourself out

They mean the same thing. They all mean: "You can go ahead and do it, but I'm not enthusiastic."

2. Why people say "you, too" not "me, too" when someone says "It was great
seeing you"?

Me, too = Seeing you was good for me, too.

You, too = It was good to see you, too.

[I edit copy and have tutored university writing.]

[bhaisahab]

Knock yourself out. That's a new one for me!

[timjphillips]

They are interchangeable in use but obviously have slightly different origins which may have a baring on the level of applicability of each.

Suit yourself: - I have no strong feelings, so please do what ever would suit you best.

be my guest: - You are welcome to do (action). - (often sarcastic or at least ungracious)

Knock yourself out:

1 - I give up, but you are welcome to try. (it may knock you out)
2 - help yourself to as much as you want. (until you knock yourself out)