I am not exactly a newbie linux user (I use mostly debian based distros for years) but I have to ask because it is a complicated question.
I have an external hard drive and I want to use it with the best way I can imagine:
It has to contain the needed partitions to be used as a live usb with enough persistent space for useful packages. I will use the way I found here (I hope this way I will have the option to install ubuntu to other PCs with the help of my external drive and to run ubuntu in any PC)->see Edit bellow
I would like to have some (the most) of the space of my external drive for backups and for any useful file I want to save and to carry. (I want this partition ntfs or fat32 to can view my files from any OS -but I am open to discuss it-)
I would like to use this disk as a backup-restore disk for my windows and so I need an ntfs partition for that because windows doesn't allow other kind of filesystem for this job.
Any other usefull partition like swap or bios-grub or efi that needed to have access from every PC to my files and to my live ubuntu
My question is: How can I proceed to make this happen?
Step by step please (include links where needed and detailed answer including the kind of partition table that would be better etc)
PS: I tried to make it featured question and give some points but probably I am too new to the "forum" :(
Edit: Finally after a discussion with @sudodus and the comments of the others, I decided that the live OS functionality of the external HD costs more and offers less than I expected... I tested the functionality of live usb with persistent storage and I found out that windows complains with many of the partitions until finding the last one that can be used as storage... This is not good for a storage device (and that functionality of an external drive is more important)... Additionally... the drive will be much slower than a flash drive and this makes me to decide to use my HD as storage device... The other expectations remaining and I am close to decide to make a Gpt partitioning and have ntfs for windows restore files... ext4 for files I can acces from everywhere and may be one or more ext4 (if i find a reason for this)