You NEED to use the amiibo AND complete the game to unlock all these features.
http://www.japanesenintendo.com/post/163362510634
Now there is some concern that the way to unlock the extra modes is to use the amiibo AND complete the game, rather than using the amiibo OR completing the game.
Let's hope NoA/NoE or the English website can clear this up.
http://www.japanesenintendo.com/post/163362510634
The various amiibo do the following in Metroid: Samus Returns...
Samus Aran (Metroid Series)
Elon Reserve Tank (special ability recovery)
Metroid II Art Gallery (unlocked after beating game)
Metroid (Metroid Series)
Metroid Marker (tells you location of nearest Metroid)
FUSION Difficulty Mode, play in the Fusion suit (unlocked after beating game)
Samus Aran (Super Smash Bros. Series)
Missile Reserve Tank (missile recovery)
Concept Art Gallery (unlocked after beating game)
Zero Suit Samus (Super Smash Bros. Series)
Energy Reserve Tank (energy recovery)
Sound Test (unlocked after beating game)
Now there is some concern that the way to unlock the extra modes is to use the amiibo AND complete the game, rather than using the amiibo OR completing the game.
Let's hope NoA/NoE or the English website can clear this up.