Apps????

As many as you like, more-or-less. Depending on whether you've got a 16, 32 or 64GB iPad will ultimately limit the number, as will - of course - the size of each app. But, other than that, there's (virtually) no practical limit (for the pedantic, yes, there are a limited number of Home screens and, yes, a limited number of folders per Home screen and, yes, a limited number of apps per folder but no one has reached that theoretical upper limit yet, as far as I'm aware!!)

Tim