I doo support the view that the best way to learn the Rules is to have a go at the Rule Book and other resources.
Regarding your question on Relief Area I have put something together" off the top". There is no guarantee that it is 100%.
Current Rules have 3 common variations.
Method: Find the Nearest Point of Relief (NPR), Drop the ball within one club length of the NPR. The maximum area for dropping would be a semicircle of 2 club-lengths diameter*. This procedure is encountered most commonly when taking relief from an Abnormal Ground Condition and Immovable Obstructions, in my experience. There are other free relief situations. I am excluding Bunkers and Putting Greens, Dropping Zones from this discussion.
*The actual available area is often less that the maximum. The common reason the NPR is smaller is the proximity of the NPR to an area in which the ball may not be dropped. Think Water Hazards, Out of Bounds, Bunkers, and Putting Greens when the NPR is Through the Green (General Area).
Read Rule 20-2 on Dropping and Redropping.
1) If dropping other than Back-on-The Line or Stroke and Distance the measured area will be found using 2 club lengths radius. The maximum area will be a semicircle of 4 club-lengths diameter.
The actual available area for dropping might be a lot less. For example think of situations that arise taking lateral relief from a Lateral Water Hazard.
2) If taking Back-on-The Line relief from a Water Hazard or an Unplayable Lie the ball is dropped at a spot selected on the visualised line. It is not dropped in a measured area. The ball will probably bounce and roll. Read 20-2c for redropping requirements.
In 2019 The 2 club-length radius will work pretty much as now for some Penalty Relief. However there is a restriction on the Club used for measuring, the drop is from knee height and the ball must be played from within the relief area.
Back-on-the-Line Relief is quite different. The Point is selected by the player on the Line and must be dropped and played from within a 1 Club Length radius. Area up to a maximum of a semicircle.
There are excellent diagrams throughout Rules 14, 15 and 16 in the Player’s Edition (hard copy and on-line).