CJ1234
Your 2)
In Europe (and US, I'm fairly sure) B757 and 767 are on a common type rating. I can't speak for elsewhere. However - after initial training on one of them you need to differences training to qualify on the other, as you do for sub-variants, e.g B767-200 and -300 series.
I did B767-200 first, the diffs for 757 was classroom (1 or 2 days), 2 x 4hr sim shared with another student, and 4 sectors line training. 767-200 to -300 was a classroom day, then jump in and fly. Not a problem.
I should add this this was around 10-15 years back, and there may have been some changes.