No Evgeny, you can not substitute after the TE with Kovtun. If you are injured after or during the TE, there will not be an entry for the individual event.
Yes they could. Tarah and Danny were required to stay up until the SP draw if they were needed due to injury or illness. That's why they name alternates for the individual events. Please show me the rules where this is stated regarding the TE and IE events. It would be completely biased and unfair, if say, Chris broke his leg the day before the IE event and the alternate was not allowed to skate. It makes no sense. And I doubt the USFS would just pay for Tarah and Danny to be there past the draw of the pair SP in the TE if it wasn't possible for them to skate in the IE if necessary. The Kovtun/Plushy example is not factual. Kovtun could have skated in the IE if Plush wd before the short draw.