1. Can't be that young. Bond was an ex Commander in the Royal Navy. That's a Lieutenant Colonel. Don't get there in your 20s. Add in a few more years of training after going into Her Majestys Secret Service and the experience to get to 007 level and you're looking at at least 35 to 38.
Fleming’s Bond joined the Secret Service in 1938 and was commissioned a lieutenant in the Royal Navy Volunteer Reserve, Special Branch in 1941 and promoted to Commander by the end of the war.
Fleming himself was commissioned a Lieutenant in the RNVR in May 1939 at age 31 (Bond is around 23-24 but Fleming changed and froze his age at various times) and promoted to Lt Commander within a few months.
promotions can come very fast in wartime, especially if politics are involved, or - like Fleming - your family connections get you a job as personal assistant to an Admiral