Reminds me NOT to trust reviews! (will be updated!)
Playing in the easiest difficulty.

In short:
1. This game is like Hitman Sniper but more... open.
2. There are many contracts/bounties in one Map. Yes, you can finish ALL of them first then proceed to exfil. These contracts or bounties are spread throughout the map in sections. So, it is very easy to 'organize' your bounties. Just find which are closest to you.
3. No, being 'spotted' does NOT mean ALL enemies will come to you like some reviewers said. Only few enemies in the area will respond to backup.
4. You can be a horny sniper (fast paced) or take your time slowly. Hitting two or three enemies with silenced weapon as fast as you can before they call for backup or open fire will not alert nearby enemies. However, if you don't hide the bodies, patrolling ones will become alert and therefore alerting more enemies.
5. Yes, AIs are intelligent. They use binocs to find you and coordinate they attacks. Such as flanking. But at some point, they just hid while i shot their team mates. Super fun!