If your Mac is still working ( I suppose so, since you mentioned "About This Mac" etc) , there's no need to use a thumb drive.
However, if you prefer to install a Mac OS through a USB, the installer should not be "copied" but made on a Mac device with e.g. createinstallmedia .
Personally I would install 10.11 El Capitan instead of 10.10 , it's known as a very stable OS version.
The only reasons I can think of to use a bootable USB installer :
- There's no OS installed on the internal drive
- You prefer to erase the OS installed and start with a clean install
Unfortunately you didnt give any details about your MBP (exact model and year) , so it's hard to guess which OS is supported or not on your machine....
Generally people choose an OS version based on compatibilty with apps and/or the last version supported for security reasons....
You can use a USB flash drive or other secondary volume as a startup disk from which to install the Mac operating system. These steps are primarily for system administrators and other experienced users who are familiar with entering commands in Terminal.
support.apple.com
Download and install current or previous versions of the Mac operating system on compatible Mac computers.
support.apple.com