I can't tell you about 2019. Did you efile or mail it? When you log into your account what does it say for 2019? Like Accepted, Rejected, Printed or Ready to Mail, etc.? If you didn't pay the Tax Due and the IRS didn't send you a bill to pay it then they might not have gotten your 2019 return. But they might still be behind in processing 2019 returns.
What year do the 1040ES slips have on them? Up in the corner? 2020 or 2021? It's too late to use them to make payments for 2020. If you have a 2020 tax due now you need to pay the whole amount.
For the Stimulus. What did you get? Did you get the first round? How much? If you didn't get the right amount or didn't get the second round you claim it on your 2020 tax return. Have you filed 2020 yet? Check 1040 line 30 for any missing Stimulus (just for the first 2 rounds, not this 3rd one).
