[RPG] How to build a demon hunter

Yes, it's possible to select Scout or Hunter powers if they have a specified level.

As a general rule, when a member of a class is eligible to select:

• an At-Will Attack,
• an Encounter Attack,
• a Daily Attack
• or any Utility power,

and a level is specified, he can select a power of the same type and of lower or equal level from any homonymous class.

So, for example, a Player's Handbook 1 Ranger may select Speed of the Zephyr^DDI (described as Ranger Utility 22) upon reaching 22^nd level.

A 1^st Mage Wizard from Heroes of the Fallen Lands may select Thunderwave (a Wizard At-Will Attack 1) from Player's Handbook 1 and vice versa.

A Player's Handbook 1 Paladin cannot select Righteous Radiance as one of its powers at 1^st level (because that power is described as a Paladin Attack). He can however, select the Strike of Hope power (because it is described as a Paladin Attack 1, that is: it has a level).

Those listed in the class shaded box are all class features.

Some class features are expressed as powers (in fact, they provide powers). Other powers are taken with the character normal advancement. I think you are interested into telling the difference between these two.
Most Player's Handbook 1, 2 and 3 classes share the same advancement in power selection (called AEDU). AEDU stands for At-will/Encounter/Daily/Utilities. All have they unique class features gained at 1^st level, but then, they all gain powers at the same pace (as you could find out on a big table in PH1).
Heroes of Fallen Lands and Heroes of Forgotten Kingdoms classes (as well as other subsequent classes) exited the AEDU paradigm by providing another approach. Class features are granted throughout the whole career, and occasionally you select powers from a list, so the difference between a class feature and a vanilla power has thinned.

However, if the distinction is important for you, you have some clues when deciding if something listed in the class breakout is a class feature or a vanilla power.

1. If the element is a power that has a level and a class, it is not a class feature.
2. If the element is found under the Class features list in the class shaded box, it is a class feature.
3. If the element listed in the class breakout has a name that ends with "power" probably it is not a class feature.

Examples:

1. Hunters and Scouts receive Reactive Shift at 5^th level. The power has the label "Ranger Utility 5" in the upper right corner of its block. Having a level, it is not a class feature.
2. Hunter class has the Disruptive Shot entry listed under its shaded box. The provided power is a class feature.
3. A 10^th-level Scout may select an Utility power (the subclass lists Eyes of the Owl, Root Gate, and Verdant Flames, but he is not limited to these ones). The class breakdown names this entry as "Level 10 Scout Utility Power". The selected power is not a class feature.

This is also a clue to when a power derives from a class feature: if it hasn't a level, chances are that it is provided by a class feature or feat.

Yes, it really is that simple.

While the main D&D 4e classes have a lot of choices, one key feature of the Essentials classes (especially the early ones) is that they make most of the choices for you.

So yes, you DO get all those awesome level 1 powers in the class table. If you were playing a PHB1 paladin, you'd get to choose some of them from larger lists, but you'd still get a ton of powers and features.

If that seems overpowered, it's by design.

As I mentioned here, 4e is about heroes doing heroic things, not ordinary people scraping up every advantage in order to survive. The mechanics want you to feel cool and capable from the very first encounter.

To this end, classes get all their iconic features right out of the gate: that leads to some front-loading of powers at level 1.