I have three question about modeling,they are all simple,but I can't find a quick way to do that.
- How can I cut a line in vertical?
It's easy to make a cut between two point,but if I don't have the second point and want to cut a vertical line,how can I do it quickly?In other software,Shift always works,but I don't know how to do in blender.More over,if I can cut them in some other direction will be better,i.e. 45°.

- How can I join those lines?
If I want to make such cross shape,I use bridge to make it.But the problem is,even those lines are on the same plane,they will not really cross,no vertice generated,two parts are just overlapped.How can I add vertices to the point where lines cross quickly?

- How can I add an even loop edge?
I have a shape shows below,I want to add a loop edge,the distance to the boundary should keep the same.I have tried Edge Slide and Inset Faces,but they are all depends on percentage.The only way works is solidify the 2D model,bevel the boundary and then delete the part which I added by solidify.Is there a quick way to do that?

Here's the simple demo. https://pasteall.org/blend/c30ee33c4e0d49b2a8bcdbdb7ca024f5
Thanks a lot.
Update,the third answer should be:1.add a face; 2. bevel the line and unclick Loop Slide in bevel settings.






