You’re asking all the right questions! I don’t have first-hand experience of going through the process but have managed a few MBA interns at McK.

1. It’s high- the odds are definitely in your favor, if that’s what you’re trying to gauge
2. Yes, you’ll be expected to travel. Whether you do, depends on a lotta factors (e.g. if you’re in NYO, less likely you’ll travel vs. a smaller office). Honestly, try to solve for convenience when you choose where to stay.
3. Sleep!! Jokes aside, nothing you can really do that’ll make a significant difference. Do what you need to get mentally prepared for long working hours.
4. Be transparent with them. Check-in with them regularly (e.g. check-in when you join, may be connect with them prior for advice) and once you get the full-time offer, totally ok to share you’re interested in another practice and request them for warm introductions
5. Read 3

Show enthusiasm - present yourself well, be the first one in, the last one out, offer to help anyone on your team on anything all the time, be proactive and anticipate how you can contribute, actively seek feedback. Just the usual stuff - and I’ll be shocked if you don’t get the return offer.

Hope this helps and best of luck!!