Mirror Edges Not Working

You have to increase output width and height (right above the mirror edges box). I personally prefer puting it on 300

You have not done anything to the settings. If you want 3 copies of your layer horizontally and vertically then you have to change the output height and width to 300. If you want to keep the layer size the same but make more copies you have to change the tile width and height. Think of those values as percentages. When you post screenshots please select the problem layer and press 'uu' to show is all modified properties. Motion tile works on layer size so if you have added a mask, you will not have edges that match up.

When you have problems with a tutorial, please post a link to the tutorial. Most of the ones you find searching the net are pretty poorly thought out and explained recipes presented by enthusiasts. A lot of them create more bad habits than good workflows.

I'm not clear what you expect. Apparently from your image the black frame is part of the clip and that means you won't see anything because everything happens outside the actual comp window. You seem to have a wrong understanding of the process. And yes, of course pplying an effect like MBL directly may override other effects, too. Your setup simply doesn't make a lot of sense. Start by actually pre-composing your clip to crop it to the desired size, then use the result in a parent comp to accommodate your mirroring. Rinse-repeat for potential issues with MBL. This is basic stuff. You should definitely read the online help. A lot of stuff in AE is not intuitive and simply cannot be figured out on the fly, contrary to your current approach of just muddling through...

Mylenium