Question in using comma

1) Susan puts some nuts on the chocolate cake in strawberry saurce which is her favour.
-- What is her favour? Nuts (direct object), chocolate
cake (indirect object) or strawberry saurce (adverb?)?

if there is a commor after saurce, i.e. "May puts some nuts on the chocolate cake in strawberry saurce, which is her favour."
That means her favour = some nuts on the chocolate
cake in strawberry saurce. right?

2) She put the card into a big envelop with a red sign.
-- Where is the red sign? the card (direct object),
envelope (in-direct object? adverb?)

-- If the red sign is on the envelope, would the sentence be:
She put the card, into a big envelop with a red sign.

-- If the red sign is on the card, would the sentencebe:
She put the card, with a red sign, into a big envelop.

3) Any book suggestion for building complex sentance?

Many thanks for your help!

Some more questions in modified cases:
(1) Susan puts some nuts on the chocolate cake in strawberry sauce, which are her favourites.
1a- Is it proper English?

1b- Is "her favourites" referring to "some nuts"? Should it be more clear to the meaning? Any other possible meaning?

(2) Susan puts a cherry on the chocolate cake in strawberry sauce, which is her favourite.

2a- Recap to Clive's reply, the meaning of (2) should be unclear. Now the direct object (cherry) is singular. Could "her favourite" refer to "a cherry"?

2b- Is "her favourite" will still inclined to be 'chocolate cake in strawberry sauce' as it is the nearest words to "her favourite".

2c- Could it mean "her favourite" = "a cherry on the chocolate cake in strawberry saurce"? if not, how to present for that meaning?

2d- If "her favourite" is just "the cherry", then "Susan puts a cherry, which is her favourite, on the chocolate cake in strawberry sauce." Right?

2e- If "her favourite" is just "the cake", then "Susan puts a cherry on the chocolate cake, which is her favourite,  in strawberry sauce." Right?

2f- In general specking, is it not proper to make such an unclear sentence? Any exception?

3.1) She put the card into a big envelope with a red sign. i.e. the sign would be probably on the envelope.

3.2)She put the card into a big envelop, with a red sign. i.e. the sign would be in the envelope.

Is it proper to make such sentences as 3.1 or 3.2? If they are proper sentences, how to distinguish the meaning in oral English as a comma is just a short pause in conversation.

Neither version (with and without the comma) is the clearest way to write the idea.  The which clause does not modify 'our country' (though 'our country' is the nearest subject in the word sequence).  The which clause may be interpreted here as modifying either 'natural substances' or 'develop natural substances'. 

Semantically speaking, the idea might best be written--

'We can be made rich by developing our country's natural resources'.

or--We must develop all our country's natural resources if we want to be rich.'

or--'Developing all our country's resources can make us rich.'

Hi,

There have been so many amendments to the last post that I don't know which are new queries. So, I'll just comment on the last part.

3.1) She put the card into a big envelope with a red sign. 

3.2)She put the card into a big envelop, with a red sign. 

Is it proper to make such sentences as 3.1 or 3.2? If they are proper sentences, how to distinguish the meaning in oral English as a comma is just a short pause in conversation. Sure, we say this kind of thing all the time. The listener may not even care about the exact meaning. If he does, he can ask for clarification. Similarly, if the speaker wants to say something where the meaning is very important, he will typically choose words that make the meaning clear, or follow up with a question to make sure he has been understood correctly.

Does everyone who speaks in your native language speak precisely at all times? I doubt it.

Best wishes, Clive

Hi again,

My comments are in  italics.

(1) Susan puts some nuts on the chocolate cake in strawberry sauce, which are her favourites.

1a- Is "her favourites" referring to "some nuts"? Is it clear in meaning? Any other possible meaning? In theory, it could also refer to the two items, chocolate cake and strawberry sauce. It'd be clearer to put the relative clause immediatley after the word 'nuts'.

(2) Susan puts a cherry on the chocolate cake in strawberry sauce, which is her favourite.

2a- Could "her favourite" refer to "a cherry"? No

2b- Or, is "her favourite" will still inclined to be 'chocolate cake in strawberry sauce' as it is the nearest words to "her favourite". Yes

2c- Could it mean "her favourite" = "a cherry on the chocolate cake in strawberry saurce"? Very unlikely if not, how to present for that meaning? I think that for clarity, you'd have to be explicit. Perhaps say something like 'which is her favourite combination of three things'.

2d- If "her favourite" is just "the cherry", then "Susan puts a cherry, which is her favourite, on the chocolate cake in strawberry sauce." Right? Yes, yes, yes.

2e- If "her favourite" is just "the cake", then "Susan puts a cherry on the chocolate cake, which is her favourite,  in strawberry sauce." Right? Yes

2f- In general speaking, is it not proper to make such an unclear sentence? Any exception? It depends on what you mean by 'proper'. To tell you the truth, if you say this kind of thing to me, I just smile because you're friendly, I smile back, I say 'That sounds nice', and I don't much care exactly what you mean.

Best wishes, Clive