So, I have a signed raw transaction with 1 input and 1 output.
If somebody gets this signed raw transaction the only thing he can do with it is to broadcast the transaction (if it is not yet broadcasted), right?

So, even if the input is signed nobody can alter the transaction to send the input to other output(s), right?

In other words:
- inputs are locked
- outputs are locked
- amounts are locked
- nobody will be able to spend the specific txid and vout to another output(s)
- nobody can find out the private key of my spending addresses

If this is true (and I assume it is), what is the safest way to check that all inputs are signed and the transaction can be broadcasted and it won't generate an error? Can I test the transaction will go through without broadcasting it?

Thanks in advance for all your comments.