Upgrade older Projects - need some advice

Hello,

i have some older projects using Drupal 8 Beta7, Beta 10 and Beta 11.
I would like to upgrade them but i have some problems where i could need some advice.

First thing :
Beta 7 based site. Initially developed using beta 4 and half hearted upgraded ( i had no idea what i was doing )
I have some entity schema updates that won't go away and think they are from beta 4 or 5.
There is this critical : https://www.drupal.org/node/2542748 which will disable automatic entity updates completely.

Now i have some questions about the best way to go on about this :

Should i wait until the critical is in and install beta2bet, then directly update to the newest version and resolve them after the upgrades or :
Should i resolve the automatic entity updates using beta 10 and then after that do the upgrades ?

Then the next question is about the way to resolve the automatic entity updates:

Is there any way where i can find out what didn't work ?
Do i need to write hook_update_N functions or does it work just changing the database tables ?

Greetings,

Rainer