eSIM for long-distance driving

It depends on the daily full-speed threshold stated on the plan page. Once that threshold is reached, speed drops until the next reset. Always check that figure before buying, rather than assuming from the word unlimited.

Only if the plan explicitly states tethering is allowed on the plan page. Check that line before buying every time, since not every plan permits it.

The plan stops working the moment you enter a country outside its coverage. Check before departure whether a regional plan covering your whole route exists, rather than buying a single-country plan when the route crosses several borders.

An eSIM still depends on there being a real network in that area, just like any SIM. If there is no network to connect to at all, it will not work temporarily. Offline maps are the fallback for that stretch until signal returns.

No effect. Once the clock starts from the first connection, it runs against continuous calendar time, not the hours the phone is actively in use, so airplane mode does not pause it.

Generally not — a profile binds to the first device it installs on. If this happens, contact the team to see what options exist for your situation.