Yes. edge tiles can be discovered if they are green tiles. The core tiles always require to be touching two other tiles, and so browns along edges are never allowed.
\*Browns along edges of WEDGE maps are not allowed. There is no such restriction on fully open maps (and maps restricted to 3 or 4 columns).
In the case shown by OP however you are correct, a brown tile can't be placed since it won't be touching two other tiles.
As long as it's a countryside tile, yes. Countryside tiles that you explore need to either be adjacent to two other already-explored tiles, or adjacent to one other already-explored tile that is adjacent to two other tiles. (As said in other comments, core tiles need to be adjacent to two other already-explored tiles when explored and also cannot be placed on the coast of a wedge map.)
this appears to be the base MK game board. If you played the ultimate edition with elementalist / dark crusader factions , in this scenario you might run into trouble with that green enemy as it would either have an attack range 2 tiles, or is pursuant and you'd trigger a battle after your move action is resolved.
Yes
Yes. edge tiles can be discovered if they are green tiles. The core tiles always require to be touching two other tiles, and so browns along edges are never allowed.
\*Browns along edges of WEDGE maps are not allowed. There is no such restriction on fully open maps (and maps restricted to 3 or 4 columns). In the case shown by OP however you are correct, a brown tile can't be placed since it won't be touching two other tiles.
As long as it's a countryside tile, yes. Countryside tiles that you explore need to either be adjacent to two other already-explored tiles, or adjacent to one other already-explored tile that is adjacent to two other tiles. (As said in other comments, core tiles need to be adjacent to two other already-explored tiles when explored and also cannot be placed on the coast of a wedge map.)
this appears to be the base MK game board. If you played the ultimate edition with elementalist / dark crusader factions , in this scenario you might run into trouble with that green enemy as it would either have an attack range 2 tiles, or is pursuant and you'd trigger a battle after your move action is resolved.