Although I can’t help you with all of your problems, I can help you on a couple.
Your second question:
To use an “Extrude by Polygon” function in Maya. What you want to do is extrude the faces, then Shift+Ctrl+Right Click and go to “Toggle Keep Faces Together”. Also, if you go to the Edit Mesh menu, you’ll see it at the top.
Your fourth question:
About the extra edge on the bevel. I‘ve never used the bevel thing before, but I think that all you’ll have to do is select those 2 edges you don’t want and delete them.
Your last question:
You probably would want to use the Split Polygon tool or the Cut Faces tool. Both can be found under the Edit Mesh menu.
Did you check out the free tutorials that are on this site? Do you have any other questions?
Welcome to the SM forum!