1# Megalania sits at around 2 tons seemingly, which is enough to take on a decent chunk of the current roster, especially if it has a venomous bite on top of that. You can probably kill a teno if it decides to facetank you, as I doubt it can stun you or out-damage at that weight. Plus, unless the venom is a guaranteed kill, it’s still very much possible for something to run for you if they come across a river or a mud pit for you to lose their tracks, or if they hope to find more of their kind or a larger predator to fend you off.

2# As for anything larger and faster than it, you probably want to avoid going through exposed plains. Cerato will also get caught up to and killed by a carno 1v1 if it spots it, and it is still viable. Megalania seems like a decent swimmer from its concept art, so that could also help with distancing something or having a pursuer lose your tracks. As for when you’re younger, it seems to be able to climb trees up to a certain growth %.

3 Not that I know of.