I think I found the answers to my questions, after some frustrating search.
All these can be entered on the "1040/1040SR Worksheet". Click on the Forms icon on the top left corner, and open the worksheet from the list on the left.
#1. Income can be reported in the section for "Schedule 1 - Additional Income and Adjustments", line #8, Other Income. I wrote a description to indicate what this correspond to. This income should also be reported on Form 8938 (Part III, 2 Other Foreign Assets - 2d Other Income), with a reference to "Schedule 1 Line 8".
#2. For Form 1040, Line 12A, go to the forms, select the 1040/1040SR Wks, scroll to the section 12a, enter the tax amount against the line that says "H Additional tax from Form 8621", in the "Tax Smart Worksheet" section right above the line for section 12.
#3, For Schedule 2, go to "Schedule 2 - Additional Taxes" section in the "1040/1040SR Wks", in the "Additional Other Taxes Smart Worksheet", enter the amount against the line "O Section 1291 interest on additional tax from Form 8621".
Hope this will help someone.
--Shibu.
