You can see the walkthrough for each Island with all collectible locations in the following videos:
(I haven't unlocked all achievements because some ot them were bugged when I played.)

Achievements :
1:21 Jump ? : Press spacebar
2:59 Gotta throw 'em all : Throw a fruit
27:07 Welcome to Lay : Restore energy to Nymphea island
27:45 Partner for life : Fly by yourself for the first time

Cristal locations :
4:16 Green cristal 1
6:37 Green cristal 2
9:16 Green cristal 3
10:19 Green cristal 4
11:25 Green cristal 5
13:52 Green cristal 6
15:43 Green cristal 7
18:00 Green cristal 8
18:45 Green cristal 9
19:42 Green cristal 10
21:13 Green cristal 11
22:13 Green cristal 12
22:53 Green cristal 13
23:46 Green cristal 14
25:28 Green cristal 15
26:47 Green cristal 16
28:54 Green cristal 17
30:35 Green cristal 18
33:38 Green cristal 19
34:42 Green cristal 20
35:42 Orange Cristal 1
36:38 Orange Cristal 2
39:31 Orange Cristal 3
39:42 Orange Cristal 4
40:19 Orange Cristal 5
40:46 Orange Cristal 6
40:46 Orange Cristal 7
41:27 Orange Cristal 8
42:21 Orange Cristal 9
42:46 Orange Cristal 10
43:08 Orange Cristal 11
43:23 Orange Cristal 12
43:53 Orange Cristal 13

Achievements :
45:18 Water is Life : Restore energy to Reimya island

Cristal locations :
0:35 Orange Cristal 14
1:29 Yellow Cristal 1
3:26 Yellow Cristal 2
3:41 Yellow Cristal 3
4:19 Yellow Cristal 4
5:02 Yellow Cristal 5
6:35 Yellow Cristal 6
7:13 Yellow Cristal 7
9:19 Yellow Cristal 8
12:29 Yellow Cristal 9
15:57 Yellow Cristal 10
16:34 Yellow Cristal 11
17:32 Yellow Cristal 12
18:46 Orange Cristal 15
19:33 Yellow Cristal 13
20:35 Yellow Cristal 14
21:18 Yellow Cristal 15
21:44 Yellow Cristal 16
22:39 Yellow Cristal 17
30:42 Yellow Cristal 18
40:47 Yellow Cristal 19
46:07 Yellow Cristal 20

Achievements :
1:40 Are you here ? Don't move for some time
26:09 Just in time ! : Get caught falling by the stingray
46:53 The ancients : Restore energy to Mont Hazetis island

Cristal locations :
3:38 Orange Cristal 16
5:01 Blue Cristal 1
6:09 Blue Cristal 2
8:26 Blue Cristal 3
10:21 Blue Cristal 4
11:00 Blue Cristal 5
13:23 Blue Cristal 6
15:14 Blue Cristal 7
20:59 Blue Cristal 8
32:50 Blue Cristal 9
34:12 Blue Cristal 10
34:58 Blue Cristal 11
36:10 Blue Cristal 12
37:17 Blue Cristal 13
39:48 Blue Cristal 14
41:49 Blue Cristal 15
43:05 Blue Cristal 16
43:49 Blue Cristal 17
48:00 Blue Cristal 18
48:41 Blue Cristal 19
49:32 Blue Cristal 20

Achievements :
4:48 Thunderstruck ! : Get yourself overloaded
5:09 No Swiping ! : Get your lightning stolen by a bernardo
53:48 That Was Electrifying : Restore energy to Windrose island
58:00 Greed : Gather all the magic crystals
59:34 Goodbye Lay : Finish game

Cristal locations :
1:43 Orange Cristal 17
2:05 Orange Cristal 18
2:32 Orange Cristal 19
3:03 Orange Cristal 20
7:59 Purple Cristal 1
8:38 Purple Cristal 2
12:01 Purple Cristal 3
13:05 Purple Cristal 4
14:59 Purple Cristal 5
17:59 Purple Cristal 6
18:23 Purple Cristal 7
27:00 Purple Cristal 8
27:37 Purple Cristal 9
28:14 Purple Cristal 10
28:18 Purple Cristal 11 (You can't see it in the video because I forgot to record :P)
30:40 Purple Cristal 12
38:28 Purple Cristal 13
39:36 Purple Cristal 14
43:30 Purple Cristal 15
46:26 Purple Cristal 16
48:38 Purple Cristal 17
53:26 Purple Cristal 18
55:54 Purple Cristal 19
56:59 Purple Cristal 20

Have Fun !