(1) Not at all. You're welcome/never mind.
2) it doesn't matter. You're welcome/never mind.
3) it doesn't matter. You're welcome/never mind.
2), can only be used in appreciation:
(1) It's a pleasure. You're welcome.
2) You're welcome. You're welcome.
My pleasure. I'd love to.
3) Can only be used for sorry answers:
(1) It doesn't matter. For example:
Sorry, I'm late. Sorry I'm late.
It doesn't matter. It doesn't matter.
(2) it doesn't matter. It doesn't matter. For example:
Sorry, I can't help you. Sorry, I can't help you.
It doesn't matter. It's okay.
Extended data:
The fixed collocation of sorry:
(1)~+ noun, an excuse with insufficient reasons.
(2) adverb+~, I'm very sorry, very sorry, very sorry.
I'm sorry to hear that, I'm sorry to inform you ... I'm sorry to inform you ... I'm sorry to say that. ...
(4) verb+~, feel sorry, feel sad
(5)~+ preposition, sorry. ...
Examples of sorry sentences are as follows:
(1) me? Felt? sorry For what? Him? And then what? His? Colleagues —? It? Must? Really? Have you been there? So what? Depressing? For what? They?
I feel sorry for him and his colleagues-it must have made them very depressed.
(2) What? What? Must? Isn't it? Do what? Is it? Where to? Sitting? Around? Where is it? Home? Feeling? sorry For what? Himself. ?
He must never stay at home and feel sorry for himself.
(3) the? Fire? Left? Kuwait? Oil? Industry? Are you online? Answer? sorry Status?
The fire plunged Kuwait's oil industry into a tragic situation.
(4) Sorry? Me? Take it with you? So what? Dragon?
I'm sorry it took so long.
References:
Baidu Encyclopedia-Sorry