Answers

2015-06-21T18:06:47+05:30
Same as that with which it was thrown ie 1000 m/s
Reason: time to reach from point of projection to the highest point and from the highest point to the point of projection will be same, since same acceleration just with opposite direction will be acting in both the cases. 
Now if time and magnitude of acceleration are same, velocity will also be same in magnitude , just the direction will be opposite
0