About line 4a missing. It is not required if line 4a is the same as 4b. Only if it's different than 4b.
See IRS Pub 590b page 22
https://www.irs.gov/pub/irs-pdf/p590b.pdf
Reporting taxable distributions on your return.
Report fully taxable distributions, including early distributions, on Form 1040, 1040-SR, or 1040-NR, line 4b (no entry is required on line 4a). If only part of the distribution is taxable, enter the total amount on Form 1040, 1040-SR, or 1040-NR, line 4a, and enter the taxable part on Form 1040, 1040-SR, or 1040-NR, line 4b.
