Putin has threated retaliate if US/UK long range weapons are used for "deep strikes" in Russia, this is a simple yes no.
1) what is the threshold for strike? For example, is poisoning a diplomat a strike? Is attacking a container ship a strike?
2) Does it have to be Putin that ordered the invasion/strike, and how certain must we be that he gave the order? What if it is against his wishes, or if he is removed from power beforehand?
@capybara i would say the threshold is that Russia specifically targets and publicly acknowledges that it was their intent. I mean an actual NATO country not a single politician unless its a literal head of state.
2) is outside the scope of this question - it should be assumed if Russia did a thing it was cause Putin willed it.
@OP that one is a bit harder - i would say in this case anything further than the current line which seems to be not further than a few klicks from the border(basically Kursk levels of depth) - if i had to be more specific basically the airfields where bombers have been taking off from or factories/industry for munitions/oil that they have so far only sent drones at.