Also, recall that command line calls are limited in size. So, if the path to TC is long and/or the pth to the project is long, consider adding TC to your system path, and creating a batch file to move to your TC project directory before using the TC command line.
Can I have multiple projects in a project suite to be run simultaneously using command line --
e.g. I would like to have project A, B and C in the same project suite to be run simultaneously, can I do that?
Unfortunately, via command line, currently you can either run the WHOLE suite or one project within the suite. To control which projects in that WHOLE suite you want to run, that's controlled via the TestComplete IDE only.