Need immediate advice on tiling my tub/shower surround. I have about an 1" lip/nail flange (1/8" thick) along my tub and need to know if I place my 1/2" hardibacker board over the flange, or do I rest it above?

I have seen suggestions on letting it rest above the flange, and letting the tile hang over the flange then caulk with silicone between the tile and tub. I am using subway tile, so only an inch of tile will be attached to the hardiback board. Is this a good process? Do I put any adhesive behind the tile where it meets the flange?

Also, I have a window about 4.5 ft above the tub and about 4 feet from the shower head, so the shower water does not spray on the window. I am planning to tile up 5 ft from the tub, which means I will tile around the bottom of the window, including about 6 in. Should I tile the window sill? Should I tile around the whole window ans sill?

Thanks for your help!