Regarding 2
Sometimes happens following scenario:
- create single account
- opt-in single account
- convert account to multisig
- opt-in account as multisig
There is example for wallet:
NAVIHNWBXL43ZV6EW6R2RY5VVIWS4Z7IHZA5UKWD
In wallet user has Symbol address: NB6DSY-BRIG75-I7W6GX-CQBGEL-MMZ3G5-SZMCKY-SRI
But opt-in tool shows: NCODC5PCSSSMYKB3RVPRDP23XMSBL3NPFH5XSKA