I have been buying bitcoin when the price was around 400$-450$.Most of my bitcoins are bought at that price around 40 BTC and remaining at less then 600$ price.i have been holding btc in paper wallet since then and already my stash in usd is 6 times.
here is one of my tx

what i want to know is please suggest some ways to invest my bitcoin at zero risk to earn some profit.Even 0.8% to 1% profit per month is good for me but it should be risk free.i don't mind the profit percentage but risk should not be there.if you have some suggestions please post that too,if i should keep holding for more years and if yes how long should i hold?
Every investment has risk, you shouls understand that. They just difffer on the level of risk. The least risk is altcoin investment and HYIP has highest risk since it always ended up as scam. There are programs in altcoin that you need to hold their coin and they'll pay your comission per day for holding that prevent them to dump the value of their coin.