MBR, UEFI, GUID questions

I have w8-32 bit, installed on a 1TB hdd with MBR partitioning. There are 3 main partitions of 100 GB each, and then the last partition has which 7 logical partitions of 100 GB each, except last one having whatever was left. PC is basically 6 years old, Intel Pentium Dual core E2180, 2 GHz BIOS is American Megatrends 0404, 1/7/2008 Now, Three questions basically - 1. I found on net that...