alone/only

[Allifathima]

1. David alone is guilty.
2. David only is guilty.
3. David is alone guilty.
4. David is only guilty.
Do all mean the same?
What are the differences between them?
Are 'alone' and 'only' used here as adjective or adverb?

[Beeesneees]

3 is grammatically incorrect.
A case could be made for 4 to be correct, but it would have a radically altered meaning.
With the emphasis (and a timbre which indicates that the speaker is shocked by the fact) firmly on the 'only', it could mean 'David has turned out to be guilty. Who'd have thought that?

The other two mean the same, but it is more usual for 'Only' to be placed before the subject, David.
Only David is guilty.
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