1: Two, one is Teacher’s Terror, that there is another is just a guess
1. I see a lot that can be brought back to MAD and I spot Teachers Terror three times. There are enough First Class Software screenshots, but from different products. Mixing two Compjoetanias is really evil 
I bet there's one left within the screenshots I did not recognize so I say: Quite sure of 2 but going for 3
2. After putting numbers on the corresponding disks I came to 18 disks with a number: 9 doubles.
3. I am quite sure of 35 screens which bring me to 21, but there are 5 screens left. One of them is probably linked to on of the first 35 which leaves 4 more than the 21 I already think to have: 25 disks.
In case I am totally wrong, I want to at least try to squeeze out a bonuspoint
: Motivation on 1 and 3:

Edit: WOOOT!!!! What happened... You added tons of questions...
I'll edit them in there... 
4. 8 disks have green in their label, be it the lable itself or the ink used on it.
5. I can see 4 3M logos. There might be more, but they're not visible.
6. I'm certain of 17, so I add one more: 18
7. Alien Slime
8. Eggbert
9. The review in MCCM 86 says that WIOS requires the following:
MSX2
V9990
MSX DOS2
Nothing is mentioned about RAM, but WIOS itself should consume 100K. Add 32K of DOS2 to that and you'll end up at 256K
10. The guys behind X-Tazy will be a kind of guess... I was led to believe that it was done by Abyss. Not sure. In case it was them:
- Maggoo
- Slayerman
- Popolon
- Maverick
- Spooky
- Mumbly
- Dandan
- Looping
11. Ace stands for Animation Club Eindhoven
12. That was An Uncle in Brazil (Damn, I gave away a lot with that overview in the beginning of my post... I've edited them out
)
13. First Class Software was born in 1986 (if not, blaim the wiki)
14. The pacman question did not land here 
15. 31 visible ASCII characters counted.
16 31 Sunrise disks were counted
2: 8 doubles
Edit: nop, it’s 9 after all. Damn you Meits.
12: An Uncle in Brazil
I wonder if it counts since Meits also listed it in his giant list, but he didn’t say which was which…
10 update: Maggoo not involved, Slayerman == Martial Benoit
15: 28 characters, 18 distinct
16 - go for 30 in the end..
(disks on 2nd pic)
13: 1988
Or 1982, if “JP Productions” counts.
5 - nobody guessed yet? 12? 
edit- @Grauw: yes, that counts
Aaand time. Dang. If only I had been home from work a bit sooner I might’ve gotten ahead of ren a bit
.
