Event Flag Question

Hello,

I am new to embedded programming and have a couple of question concerning event flags( I sure these are prob dumb questions but I havent been able to find the answers)
It says there are 16 flags assigned to each task when a task is created. Are these flags numbered by bit postion or by value ?(i.e 0x0001 to 0x000F or 0x0001 to 0xFFFF) The second question is do I have to call os_evt_clr after the receiving task receives the event flag to be able to resend or does the receiving task clear it when it receives it? My final question is there a way to signal multiple task at the same time ? i.e something like

#define Error_Flag 0x0003

__task void task1 (void) {

..

os_evt_set (0x0003, (tsk2, tsk3, tskxx));

or it has to be done as

os_evt_set (0x0003, tsk2);

os_evt_set (0x0003, tsk3);

os_evt_set (0x0003, tskxx);

..
}