No, it is not very difficult. You just run around and smash kaiju. The only semi difficult thing is using the shop to by the power ups but when you click the item name it tells you who it is for

I, too, have jumped onto the All Rider Generation 2 train. I'm enjoying it so far, having just beaten Ouja. It's steadily convincing me that I need a new DS, though.

Well I found all the unlock codes.

could you share them

Ok

These Passwords unlock All Riders in All Kamen Rider: Rider Generations 2 (No Shadow Moon code)
Rider 1- B4KECSHM
Rider 2- Q7EBKS32
V3- F3AZ58PW
Riderman-　X5SFW9CH
X-　N7XZBHPQ
Amazon-　D5V4KPQJ
Stornger-　A9HG8BDC
Sky Rider-　Y2BQ5RE8
Super 1-　B73GFMCY
ZX-　Q9V8K53T
Black-　B2G8EQYH
Black RX-　C97HPJZ6
Shin-　X8H7SGFR
ZO- W27YCMAT
J-　J83BHEDM
Kuuga-　R9G7S8DW
Agito- G8FWRK4Y
G3-X-　S4LE53CM
Gills-　T64YPSQL
Ryuki-　K7EVXH8J
Knight-　V546QFNH
Zolda-　V2GZU7RT
Faiz-　T3EZ9F2H
Kaixa-　T63DCLK7
Blade-　Z7ECMAX3
Garren-　B38E94M6
Chalice-　R42NSYBQ
Leangle- W82ABSHN
Hibiki- X4ZMQHDL
Ibuki-　D3WYK4NM
Todoroki- C3VQ8K7T
Zanki-　M29D8XFJ
Kabuto-　H34JNRBU
Gatack-　D2WXR7HG
Den-O-　V9BZMYNQ
Zeronos-　T5C2FUKN
New Den-O-　R4WAXZB7
Kiva-　D823KGNV
Ixa-　P6LD5FV4
Decade-　N268CJZS
Diend-　X2Y3U4P6
Kiva-la -　F567XTEU
W-　N2GJQ3AS
Accel-　P29A5VDL
Skull-　Z49VJ62S
OOO-　P4SQVL9R
Birth-　B378M4CY
Prototype Birth-　　E2JLUDWR

Thank you
spoiler
Also shadow moon was not in the game so i didn't expect a code for him