With the Tier 5 Youth Mobility Visa, if I turn 31 next week, and pay for all the application today, once I get all my paperwork approved, will I be able to enter and re-enter the UK for the defined 2-year period of the Tier 5 Year Mobility Visa (as I will greater than 31 (32 and 33))?
Yes. You must be " under the age of 31 on the date your application is made." . My emphasis