What happen if i stop FSMone RSP? I plan to invest $2000 in an US ETF per month for 4 months. Total investment amt will be $8K then i will stop RSP. Is that allowed? Or must I consistently put in money every month?

You can stop your RSP anytime before 6th of every month. However, I will recommend against putting 2000 every month for 4 months as you wouldn't take advantage of DCA. Especially now that S&P500 is at it's peak, it's better to space our your monthly contributions. Just my 2 cents!