For a EeeTop_PC_ET1602. What is the most recent or safe os i can run "safely" ?
Final user will be 14 years old, for work only ( word and internet ).
Xp look like a bad choice with EoL and EoS.
Based on my own use the past two-plus years, I'd recommend Kubuntu 14.04 LTS. It is similar to Windows XP at the "naive user" level (everything can be done through the GUI, and core system functions require password entry; can be set up to require admin access for those), looks good, and runs well on older hardware (I've got it on a Core2Duo 2.1 GHz laptop with 2 GB RAM and 60 GB hard disk, and while it's not a gaming system on that machine, it does run reliably and more than well enough for word processing and Internet browsing). There's another two-plus years of support (until April 2019), and an easy upgrade path to 16.04 LTS at EOL.
As a Linux distro, it's also more inherently secure than any older version of Windows can be. Learning a non-Windows OS is also a good expansion of horizon for a young person -- and programming is very easily accessible, if the youth wants to learn coding. C, Python, and multiple other languages are installed "out of the box", unlike any current version of Windows.