is it possible to adjust my light cycle?

currently I am on at 10am and off at 10pm. can I switch this to 7am-7pm and how can I do it?

No, they will die almost immediately if you turn the lights off.

Of course its alright. Just don't do it too often.

Just my opinion but I would leave them in the dark for 33 hours then start your 12/12 again. I believe that extra dark during flowering has less bad effect on plants than extra light.