Hello Gayashan Amarasinghe,
I will try to answer your questions:
A1- First I must say that you can click on the "?" question mark near the title e.g. "Execution options... (?)" and see a help text. I know that this helps may be some times may need updates or are not clear enough.
Based on: Here you select other VPL instance to be the base of this one. Then some features are taken "dynamically" from this other instance:
Take all the execution files. If you write new ones with the same name, the last are taken, except for the predefined scripting files (vpl_run.sh, ...) in this case the new are concatenated.
Take the description, but if you write new description then they are concatenated.
Take the limits for the execution resources and the file size.
Run, Debug and Evaluate: these switches allow that this options be available in the editor to the students.
Evaluate just on submission: the submission is evaluated (run the script that evaluate) when it is uploaded. This action only happens when you upload files in "submission" option but not in the editor.
Automatic grading: This switch does that the information taken from the evaluation will be takes as "grade" and not as "proposed grade". The grade is done without teacher review.
A2- No. This is not possible at this moment. But this feature is at first position in the TODO list. This will be a feature in the next VPL release.
A3- No. Notice that the limit is the environment of execution and the politic of "execution without leaving a trace in the jail server". In the case of MySQL you need to install a server with user authentication or a server for every run.
Best Regards,
Juan Carlos