Other financial discussions

Another questions on single owner LLC:

Is it mandatory  to take a self employment pay?  If so, I have retired with a government pension and with Medicare but not SSI pension.  Do I have to pay for SSI & Medicare tax as well? 

 

Assuming I have losses in LLC when first started.

I have loses in carryover from past years  stock trading that I can deduct $3,000  from my AGI,  can I also deduct losses (how much is the limit?) if I have LLC losses?