The solution to #1 can be handled 1 of 2 ways.

Option 1 if you are familiar with the programming interface you start in program 11-15-12 and set up a button code for extension swapping, then go to program 92-05 and set the extension swap password, upload those 2 programs, if using webpro no upload needed. Now go to to extension 105, hit speaker enter the extension swap code from 11-15-12, it will ask what extension you want to switch with so enter the extension you want the phone you are at to become, then when it asks for the password use the password you assigned to the extension in 92-05 and you should you may need to physically swap phones or labels depending on what the swapped extension was or had programmed.

Option #2 is to go to the block and hope and pray that no one has done what outlined in Option 1, and the installer properly labeled the block and physically move cross connect wires.

As for you problem on number 2 more info will be needed. From the sounds of it you want calls to be routed to a hunt group from auto attendant. Now do you want these calls to eventually land in a mailbox or just keep ringing? Can it ring all the phones in the huntgroup, or does it have to be individually for a set amount of time? Honestly I would set up a Call coverage key on Button #25+ set it to ring and make it auto off hook answer and call it a day. You would set the call coverage key to the virtual extension of the hunt group, doing it this way you can then have a mailbox for each huntgroup that you could assign the key to one person or all in the huntgroup to have a VM key for that virtual extension and you could get messages on any missed calls. But this is just my $0.02