Minigames: Saving times on minigames is almost entirely luck-based. Most of the games have a set timer and the game only ends when that timer runs out. However, there are certain minigames that will end quickly once you complete them. These include Sprout, Fit, Type, Solve, Move and Find (maybe). Hurdle also does this but only if you fail. Since you can complete these games (except Hurdle) quicker on Easy, this is the best section to get them on. The other games always take the exact same amount of time, no matter how quickly you complete them or even if you fail. This means you don't really have to worry about being good at the games as long as you have two lives (so you can fail Hurdle) at all times.
Most of the minigames are always played out in the same way in the same section (e.g. you will always type 'Egg' on Easy with the Type minigame) so, after a bit of practice, you'll rarely fail.
Jump: Jump is the first 'boss' minigame and, like most of the minigames, it seems to take a set amount of time every time so there's no need to worry about playing well. Just jump at the edges of the platform and avoid walls when the water is rushing you back. It is generally ok if you just clip one of the walls except for the last wall that comes out from the bottom. If you hit that, you die. Dying here basically means you should reset, even if you got good minigames on Easy.
Stomp: Stomp is the next boss and arguably the most difficult and will definitely take some practice to get a good route. When falling down, try to avoid the enemies as hitting them will slow you down and it's generally not worth doing it to try and clear a path. When you hit the bottom, try and land right on the egg on the right side of the screen as this stops an animation of the duck walking to get the egg. On the way up, I'd recommend using the jellyfish enemies to give yourself a boost as these don't move. Try to bounce off as many enemies as possible as this makes you go faster than the platforms but is also more dangerous as you can hit into other enemies. If you do get hit, don't panic and try to land on a platform or another enemy if you can. It's very easy to go into a combo of being hit and fall into the lava, if you do, you should probably reset unless you want to practice some more.
Blast: There are six tanks to start with. Head pretty much straight down and hit the first one on your left. Keep going down and there'll be another two. Then head right and you'll find another tank. Keep going right and a little up to find the fifth one. The last one may be a little up from there but it also travels the maps sometimes so you may have to search for it. When doing this, try to move either up, down, left or right as diagonals slow you down. Once the six tanks are killed, Giga Goose will spawn. It can either spawn in the top left or bottom right but, if you haven't had to search for the final tank, it should spawn in the top left. Head to the very top of the map so that you're to the right of Giga Goose. Here you should have a lot of room to move around and the goose will be trapped between two walls. If you keep moving, it'll be difficult to get hit so you can just keep shooting at Giga Goose.
It's probably easiest to see how to complete blast by watching my run:
