magisterludi wrote:can I perform all the updates together (UP6,UP7 and UP8)?
Yes, but be absolutely sure to read the UP notes
before the upgrade. UP6 is already in your system, so read the notes on UP7 and UP8.
magisterludi wrote:Or is it better to wait for the new ISO to be released?
It's better if you don't want to download a gigabyte of updates after the installation. Also the new installer will probably have the support for EFI and GPT, so if that matters for you, I'd suggest to wait.
magisterludi wrote:I installed LMDE on a my friend's PC because I think it's a simple and complete distro but if there will be problems I think that he could not have a positive impression and the hard work done to convince him to use linux will be lost.
LMDE is not recommended for newbies, as it's clearly stated on this page
- You don’t need to ever re-install the system. New versions of software and updates are continuously brought to you.
- It’s faster and more responsive than Ubuntu-based editions.
- LMDE requires a deeper knowledge and experience with Linux, dpkg and APT.
- Debian is a less user-friendly/desktop-ready base than Ubuntu. Expect some rough edges.
- No EFI, GPT or secureBoot support.
Of course he will not have a positive impression when something breaks on the next upgrade (and things can break, we can't test every possible case). I recommend giving him Mint 13 LTS, it's stable, supported until April 2017 and easy to use.
magisterludi wrote:What is the most safe method to update starting from the distro as it has been released about a year ago?
It doesn't matter when it has been released. The safe method to upgrade is posted in the blog every time a new UP is released. The latest post is here