I agree, a Form 1099-R with codes 4 and G in box 7 issued to a non-spouse beneficiary can never have the IRA/SEP/SIMPLE box marked. (A surviving-spouse beneficiary could conceivably receive such a Form 1099-R for a direct rollover from an inherited IRA to the surviving spouse's own 401(k) or similar qualified retirement plan, but I've never heard of that actually being done.) Given the circumstances, my guess is that this was a non-reportable trustee-to-trustee transfer of an inherited IRA and the IRA custodian misused form 1099-R. Despite the IRS issuing instructions in 1978 that such a transfer is non-reportable, many smaller IRA custodians make the mistake of trying to report it by misusing the codes for box 7 of a Form 1099-R as seems was probably done here. This misuse of Form 1099-R does seem of have subsided somewhat recently but seemed much more common 5 years ago.
Assuming that the account was originally an IRA, you must make up any missed RMD that your father had not taken for 2012 and beneficiary RMDs beginning in 2013 based on your life expectancy in 2013, reduced by 1 each subsequent year if you were the beneficiary designated on the IRA or based on your father's life expectancy in the year of death, reduced by 1 each subsequent year if your father's estate was the beneficiary and you inherited the account through the estate. You must also file a Forms 5329 for each year that you failed to take the RMD timely, as macuser_22 indicated.
IRA custodians are under no obligation to notify you of your responsibility to take RMDs from an inherited IRA the way they are for IRA participants.
Note that by operation of law the IRA became an inherited IRA for the benefit of the beneficiary upon your father's death. The fact that it took until 2015 for the account to be officially titled as an inherited IRA doesn't change that.
