Soviet reconnaissance, artillery, and Air defence

[PincerDK]

Somewhat. The Forward detachment (or Operational Manuever Group as it is sometimes called) is not so much meant as an economy of force, recon, security and freedom of movement measure, but as a "Strike Force" dedicated to taking a single objective. What that objective might be and how far in the enemy rear it resides depends on the scale of the forward detachment. A Motorrifle Division using its Tank regiment or independent Tank battalion might be using it to strike for a critical bridge or piece of ground in the divisions immediate area, while an Front might use an entire Tank Army waiting to strike for an important strategic objective.

Correct, although even a Forward Detachment has its own security measures, which equals that of an Advance Guard.
But its main task is still acting as a "Strike Force" as you put it.

Actually, have you ever heard of regimental battalion sized forward detachments? or divisional regiment sized forward detachments? I know a division can form a battalion sized FD and an Army can form a regimental sized FD.
I read somewhere, that those options are possible, although it depends on the commander.

The BRM equipped units will also use their ground search radars

Have you any idea on how those works?

1. Is it better to have sources about Soviet Organisation before 1991 or after 1991? I know after the Cold War, much information from the Soviet Army was published.

Depends on the timeframe you are looking for information on ;)

During the 80's ;)