Yes.
Yes.
Perheps.
No. The game features zone-based PvP with distinct boundaries. When approaching PvP-enabled areas, players are notified through clear interface warnings.
Upon detecting a sandstorm (signaled by darkening skies and rising winds), immediately seek shelter in a rock cave, pre-built base, or any enclosed structure.
To swiftly find spice eruptions, utilize a Spice Probe (unlocked via the tech tree).