the CTC doesn't go into effect until 2021 but advance payments should start around June or July 2021. as for refunds for UC. no one, not even the IRS can tell you. there are millions of unprocessed returns. at one point the IRS stated that it might take all summer to make refunds to all taxpayers who filed returns that did not reflect the nontaxable UC. do not submit an amended return that could actually delay your refund.
if your state has an income tax see this link for what to do
That CTC increase is not for 2020; it is for 2021. Your 2020 return does not have to be amended for it. More information will be available soon; the details of how it will be implemented have not yet been clarified fully. There may be monthly payments going out beginning in July 2021, with some of the CTC still left as a refundable credit on your 2021 tax return next year.
https://www.irs.gov/credits-deductions/advance-child-tax-credit-payments-in-2021