Will IRS reject return on 3 pages or penalize me for it? Or will IRS simply accept return on 3 pages instead of 2 without comment?
Yes this year the 1040SR is on 3 pages.
The 1040SR started in 2019. It is the same as the regular 1040 just larger type and the Standard Deduction chart is added to page 1. But has the same line numbers. You automatically get the SR if you or your spouse are 65. If you are using the Desktop program there is a way to force the one you want.
If you use the Desktop program you can switch to forms and the Info Wks part II has a selection to select 1040SR or not. You can not change it in the Online versions. In the Online version if you want to use the regular 1040 form, you can print out the 1040SR and copy the amounts onto the 1040 and then mail your return.
Compare them
1040SR https://www.irs.gov/pub/irs-pdf/f1040s.pdf
1040 https://www.irs.gov/pub/irs-pdf/f1040.pdf
1040/1040SR Instructions https://www.irs.gov/pub/irs-pdf/i1040gi.pdf
The IRS Form 1040-SR and the IRS Form 1040 are exactly the same form except that the SR form has a larger typeface. Due to the size of the type the SR is three pages instead of the two for the standard Form 1040.
Form 1040-SR is for taxpayers age 65 or older who can benefit in reading the tax return with the larger typeface.
There is nothing to correct since the 1040-SR is an authorized IRS tax form.