Each level has different criteria and you have to finish the level for it to count
Unfortunately theres no great solution for these only, practice, practice, practice. Ignore everything else on the level just go for requirements and take your time.
Level 10: Collect all arrow indicators without losing a life
Took me alot of tries
A few tips :
Get to know the level best you can. The grabber nearest the arrow indicator isn't always the best one to use sometimes its better to throw from a distance to get the right angle without going too close to the electric blocks. For some arrows you will need to bounce slinky of the wall or just direct him left and right a bit.
Throw slinky from the grabbers "underarm" its far easier for aiming
Reverse direction a couple of times to slow the grabber down so your not always throwing at full strengh. For some if the grabber does a full rotation you'll throw too hard.
Level 11: Collect all the balloons without losing a life
You'll need to keep tapping the left and right mouse buttons to stop slinky spinning on the grabber and hold him in place while you wait for the flames to move out of the way. Just takes timing but not as hard as it first seems.
Level 12: Collect all the balloons without losing a life
Again just timing and practice, tap the mouse buttons to slow slinky and get your aim right, throw underarm. Found this the easiest of the 3 got it first try
If you having major problems getting these without losing a life you can finish the levels to get the bonus stage to appear. When you find the secret item and finish the stage you will be awarded protections, giving you mistakes before you lose a life. 1st bonus stage gives 3, 2nd 5, 3rd 7., 4th 9 They arent stackable so go for the 9. You can replay the bonus stage for another 9 every time your protections run out