check my current Ubuntu version through the command-line

cat /etc/*release

lsb_release -a

cat /etc/lsb-release

CPU Usage Percentages in Multicore CPU

Since you have four cores at your disposal, maximum CPU usage would be 400%, or 100% of each core presuming that each application is intensive enough to make full use of each core. This isn’t often the case however.

Using Photoshop as an example again, it may maximize one core at 95%, or thereabouts, while saving or editing a high-definition image. It is unlikely to spread power to more than two cores in any case. This would be similar for other image editing programs.

Running instances of multiple high-quality videos will likely use less than 25% of each core. However in the case of using editing or capturing programs, such as Windows Media Encoder or an intensive program like Panorama Factory, you will likely take advantage of all four cores and it should result in relatively high percentages. Rendering and encoding applications are mostly the ones that are optimized for a quad and will likely use full resources.