You failed to return a value in the else case:
public Boolean DetectPlayerAndGround1Collision2(/*snip*/)
{
if (/*snip*/)
{
if (/*snip*/) { return true; }
else if (/*snip*/) { return true; }
else if ((/*snip*/) { return true; }
else{return false;}
}
else
{
return false;
}
}