Can't imagine what could have happened just changing the belts. The screeching sound could be one of the tensioners not turning. If it runs even for a second the timing has to be close on the left cam at least.
Not if you didn't turn it with the belts off. If you did and happened to set it on T2 and the up marks on the cam pulleys up it would throw the ignition 180 off and it wouldn't try to start at all, otherwise no harm.