Ok, I'm done with this game and here is why: lags, bugs & glitches. Here they are:
1. I am currently stucked in day 76/77 and cannot proceed, because when i am almost finishing the level the last 1-2 enemies do not show up. Personally I don't blame them, who would like to get killed? I wrote in day 76/77, because I am not sure on which day I really currently am. Few times after completing the day it brought me back to the same day, over and over. I was feeling like taking part in the "Groundhog Day" movie ;-)
2. The game has not only the "time problem". Few times when I was near the end of the day the game just frozen and I couldn't do anything about it but to reload the game. What was even weirder, one or two times the game gave me back the "stolen" day by adding one to the total number.
3. I confirm that the "Power Gun" medal doesn't unlock.
4. A minor bug: many times when the ghost gun disappeared, its bullet/missle just stayed on the map just floating towards the base.
5. Another glitch: indeed sometimes the rocket damage upgrade button is unclickable.
Somebody wrote earlier that the ghost gun upgrade ends too fast, I disagree. That's because with fully upgraded ghost gun between level 45 and 55 the game simply starts to play by itself, I mean if you pick enough ghost guns you can simply watch them doing your job with your minor help. From this point the game is extremely easy and boring. You even don't need the bombs anymore.
Summarizing: if this is the fixed version, it needs to be double fixed. Without those glitches I could even give it 4,5 stars, which I hope I one day will be able to do.