try to recalibrate esc.
if you still only have reverse then your fets are blown on your esc.. its not the rx like u said in your posts.if and tires spinning create no voltage.its purly esc problems more than likely you cooked it with new batts
You need to check the bec wires and contacts to see if you broke a wire .do you have a vom and the ability to use it ig so check for volta thru 2 wires only -/+. you can pull cent leed of rx plug from esc and add a receiver battery.. can be purchased or made with servo wire and 4 AA batts in...