You can check for an entity in a radius using the 'does entity exist in [radius] box' function, which is found at the bottom of the world tab.
Checking for blocks is harder, but you can use the built in 'check for block in 6*6*6 box' procedure template, which will work for most purposes. If you just want to compare two blocks, you can use the block comparison function in the logic tab.
You can check for an entity in a radius using the 'does entity exist in [radius] box' function, which is found at the bottom of the world tab.
Checking for blocks is harder, but you can use the built in 'check for block in 6*6*6 box' procedure template, which will work for most purposes. If you just want to compare two blocks, you can use the block comparison function in the logic tab.