Hi Anand,
WRT 1) are you refering to a longer running task on your created process/flow that is interrupted due to a server outtake? in that case you can use the jbpm-console to trigger a continuation or restart of that process. outherwise you should be abe to access the next human task through the console just fine. If neither of these cases please elaborate what you are refering to.
WRT 2) I don't understand. We have set the hibernate.hbm2ddl.auto property to "update" and just continue to use the sequence created on the first run - seems to be a DB issue - what DB are you on? If you use just one session (1) you should be just fine and may reuse the session on the restart.