1.) "You had a party--who all was there?"
Never! "You had a party--who was there?" No all at all!
2.) "You went different places--where all did you go?" 3.)
Rarely, more often, You went different places--where did you all go?" 3.) (the all got moved closer to the verb)

3.) "You had plans with a friend--what all did you do?"
Rarely, most often, the all gets dropped-- sometimes it gets moved as in sample 2
"You had plans with a friend--what did you (all) do?"

and the you all structure never gets slured to y'all --each word is seperate, and the all is un-accented.