You are right, if you had copied a wrong one then that's your fault or any missing figure or letter, and position intetchanged.
Bitcoin addresses have a built in checksum, so if you change a character, drop a character, add a character, swap two characters, etc., then the address will almost certainly be rejected as invalid. The checksum is 32 bits, meaning there is only a 1 in ~4.3 billion chance of a mistake still producing a correct checksum.
Receiving multiple transactions with one address is fine until you spend with it.
Not really. If I hand out the same receiving address to my employer to pay my salary and a co-worker who owes me $5 for lunch, then my coworker can now see how much I get paid.