There is no income limit on ROTH conversions.
A Conversion is from Conventional IRA to a ROTH IRA. Re-characterization if from ROTH back to Conventional IRA.
Your Conventional IRA generally has no basis. None of the money in the account was included in your taxable income unless you made non-deductible contributions to your IRA. When you convert it to a ROTH all of the money converted is taxable.