Is there any (legal?) difference between the following:
1a. The police accused him of robbery.
1b. The police charged him with robbery.

Thanks in advance.
Yes, 'charged with' is the formal, legal accusal. I don't believe you would see sentence (1a)-- the police don't 'accuse', they 'charge'; on the other hand, your neighbors would 'accuse', not 'charge', you.
There is a slight difference. The words accuse, arraign and charge all have different uses in legal-speak:

"The accused is arraigned and charged with murder."

Accused, noun, the person being charged.
Arraign, verb, the act of calling someone before a court.
Charge, verb, the act of blaming someone for a wrongdoing.
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Thank you both.
so, blame so. for sth.

should be totally different?
'Blame so. for sth.' is non-legal. 'I blamed my sister for setting fire to the cat.'
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I DO like your examples...