Ok here is the question regarding 3rd edition Shadowrun.
An adept cannot have more levels in a power than the adept's Magic Attribute. For example, and adept with Magic 4 cannot have more than 4 points worth of power, none of which can have more than four levels.
During game play, adepts may purchase additional Power Points at a cost of 20 Good Karma Points per Power Point.
Page 168 Shadowrun 3rd edition rules
So how are you supposed to purchase more power points if you can't have more powers than magic attribute?
The way I interpreted that rule is that adepts aren't restricted in the number of power points they purchase - but after a certain point they might not be able to spend them.
Let's look at the above example, an adept having a Magic Rating of 4. This means (s)he has 4 power points to spend on powers. (S)he could purchase Killing Hands, or Magic Resistance, or Improved Physical Attribute, or any other combination of powers as long as (s)he does not exceed a total cost of 4 power points. In addition, none of these powers can have more than four levels; so they couldn't get 5 ranks of Pain Resistance, for example.
If the adept purchases another power point (by spending 20 karma), they can use it to gain extra powers - but they still can't exceed four levels in any one power. So they could end up with Improved Reflexes 3 (which costs 5 power points), or they could have Pain Resistance 4 (2 points), Combat Sense 1 (1 point), and Enhanced Perception 4 (2 points), for example.
If the adept initiates, it increases their Magic Rating by a point (to 5) and would also give them an additional power point. Thus in this case they could have up to five levels in a power.
Why initiate? To get a Magic Rating of 9 and have Pain Resistance 9 - don't get any penalties until you're unconscious... It also costs less than 20 karma per level (at least for the first level if self-initiating, or to level four if group initiating, not including ordeals).
As for spell-defence, Fortune's comment stands for SR3 as well. Page 160 of SR3 explicitly states "While adepts and mundanes can learn magical Background Skills, they cannot manipulate mana and cannot use Active Magic Skills"
Adepts can't get spell defence, but they can get the power of Magic Resistance for a cost of .5 power points per level.
Kid, I thought 'groggies' referred to Aspected magicians? The 'half awakened' part refers to their ability to only use one magical skill (usually Sorcery or Conjuring).