I have a lot of questions about how to repair a broken system. I have already read a lot of things on your forum.
As I did not want to mix different questions with different answers I am going to open a thread for each subject.

Before system got broken :
uname -a
Linux linux-u6go 4.4.104-39-default #1 SMP Thu Jan 4 08:11:03 UTC 2018 (7db1912) x86_64 x86_64 x86_64 GNU/Linux
Hardware info : http://paste.opensuse.org/80894240
--- ! ---
From that thread : http://forums.opensuse.org/showthrea...-boot-scenario

Question 2-a :
step 18 show the list of EFI boot entry.
If I see an entry for my opensuse installed system I have just to verify the boot order. Then eventually set it accordingly as shown in step 19 is not it ?

Question 2-b :
I imagine that there is a reboot between step 19 and step 20. So I suppose that if system reboot normally it is useless to do step 20 is not it ?