How can I know that a particular sentence has the meaning of request or permission.

May I go out.

Shall I prepare tea for you.

I mean by reading the sentence how can I come to know that particular sentence is for request or for order.

I'm not sure that there is a simple answer to this one, Hanuman. Certain structures are normally used for requests-- can you, could you, would you; can I, could I, may I, might I; can we, could we, shall we.

Other structures are used for orders-- shouldn't you, hadn't you better, oughtn't you.

But choice often has much to do with context and paralinguistic accompaniment. If your co-worker says, 'would you close the window?', it is probably a request; if your boss says it, it is probably a command. The word 'please', facial expressions and gestures also contribute to the difference between a request and an order.
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Would I make a cup of tea for you.

Could I make a cup of tea for you.

May I go.

Shall I go.

Which one is correct?

One more thing, some times modal verb for request or other for permission.How can I come to know that it is for request or for permission.

A request (for permission) is a question, Hanuman; giving permission is a declarative statement.

'May I go to the bathroom?'
'Yes, you may.'

X 'Would I make a cup of tea for you' -- this is incorrect, as you will see from the list of forms I gave you in my previous post. 'Would you make a cup of tea for me?' is OK as a request.

'Could I make a cup of tea for you?' -- with the question mark, is an 'offer', not a request; however, they are based on the same courtesy: 'is it OK if?'.

'May I go?' -- again, with the question mark, a request.

'Shall I go?' -- again, with the question mark, either an offer or a simple inquiry about the listener's wishes.
the whole sentence " would i make a cup of tea for you" and "would you make a cup of tea for me" not depends on the grammer.

it's all matter if you pronounce the words in right intonation pattern.you must use of right intonation pattern because meaning conveyed beyond the bare words and grammatical construction.

grammatical request and intonation is different.
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