Yes, there are lots of ways. You just have to think. Put the player that died name in an array, database, or YAML file, then kick them(Optional) Use PlayerLoginEvent or PlayerJoinEvent to prevent the player from joining the server if their name is in the array, database, or YAML file. After your desired time, take the name off.
Yes of course there is. Just use https://forums.pocketmine.net/plugins/timerban.277/ look at the public functions https://github.com/onebone/TimerBan/blob/master/src/onebone/timerban/TimerBan.php write a small quick plugin or even modify timerban itself to ban PlayerOnDeath
As far as I know PocketMine includes that feature by itself, at the difficulty you can choose hardcore.
oh oke but arent there many plugins about that? He also could use TimeCommander and set the ban and pardon commands there