I followed the procedure but i forgot to unscrew the freestroke screw first

My question is. Can the hose be disconnected and reconnected without fitting a new olive?

Yes, done it plenty of times

I’d be tempted to have a spare to hand, just in case

is there any way I can bleed the brakes at the top a little?

If you remove the wheel and pump the lever until the pads hit each other before disconnecting the hose at the master cylinder end) you can shorten the hose, re-connect it, remove master cylinder lid then push the pistons back into the caliper. Any air that has entered the hose will be pushed up into the reservoir as it should still be at the top end. Pump the lever until pads touch again, push pistons back in and repeat a few times will push any air to the surface. Check that caliper pistons are all the way back, top fluid up,fit diaphragm and lid, job done.