Imp can "trash a card you access", so….

1) you need to declare you're going to use imp just before accessing to use the ability

2) you could decide to trash card using Imp when you're accessing looking at the card

If 2 is true, then let's say you could access 10 R&D cards and decided to use Imp half way through the fifth card, so the fifth card onwards are trashed or all of the 10 cards are trashed? Or it only trash the single fifth card?

You decide to use Imp when you access a particular card. And it will only trash a single card for each use.

Thanks!

I thought the ability is same as demolition run.