You put a web page location in the image tag rather than the image location. If you go to the gallery page showing the image you want then right click on the image and select "Copy image location" or something similar. Then paste this in the img tags in your message then the wonders of the interoweb will display the image in your post.
The only ''official' problem i have done that isn't in the guides
Yes the image should show in preview. I'd say around 500-600 pixels wide for landscape and 300-400 pixels wide for portrait.
For a bonus point, do white ladder from a sit. Adds a few interesting and quite tricky moves. 7c
the top move is a big leap, thats how its done. Its blind putting your feet on
I believe for the full approved tick, one must grab the true apex
A sit start exists and is supposed to be 7c but seems pretty contrived