Need help detecting block sides and adjacent blocks.

So my biggest issue currently is not being able to detect if there's a block next to, or just detecting a block face.
1. I'm trying to create a ladder block, already made a model, made the hitbox correct, but I want it so you can only place it against a wall- not free floating in air but I don't know how to detect a block behind it.
2. Also trying to make an item light blocks just like a flint and steel- however this doesn't light the sides of the block.

Anybody know the solutions for this?