Multi-Org and OATM for R12 Upgrade

Lets say, 11i (11.5.10.2) environment is planned for R12(12.1.3) upgrade. we are in the process of evaluating and planning 11i environment to 12.1.3 upgrade.

In Our case, 11i environment is meeting minimum extended suport patch level and are at ADI.7 and database is on 11.2.0.3

a) Does 11i (11.5.10.2) needs to be converted to multi-org for upgrade of 11.5.10.2 to 12.1.3?

b) Should 11i (11.5.10.2) environment database 11g (11.2.0.3) should be converted to OATM to upgrade to 12.1.3?

Does step a) and b) manditory for upgrade of 11.5.10.2 to 12.1.3?

Can we upgrade 11.5.10.2 to 12.1.3 without steps a and b? what are the implications?

Thanks,

Sai