Glass mosaic tile help?

hi everyone! i’m about to start tiling my bathtub area using 1″x1″ glass mosaic tiles on 12″x12″ mesh. what’s the right way of butting on the inside corners? and also how about the 1/4″ gap between the hardibacker and tub? should i overlap the tile on the board? by the way, i applied caulking between the board end and top of tub. will the thinset adhere to it? thanks!