[mothered]

so I can just order (with a different account and address) a cheap chinese phone with a similar weight to say that it is what I just received ?

Correct.

Be sure It's a stock Item of theirs.

what maximum weight difference it require ?

To play It safe, no greater than 40 grams.

How long must it be between the receiving of the "wrong item" and the receiving of the "good item" ?

At times, packages are delayed In transit, so It's the order date that's of relevance.

Try and purchase each Item as close as possible.