Hello
Answer for question #1 - i don't know... May be authors...
Question 2 - in original version this types of I-16(18 & 24) were wrong, in pack they corrected.
#3 - Yes, this is Ranwer's mods in new slots.
PZL-37 and CANT don't flyable, because i can't create working cockpits for them. May be later - or may be you...
#4 - there is a bug in older version... There's a new version beside of post.