If I set nSequence to be 0xffffffff and broadcast that transaction.
I think this is a regular transaction cause the nSequence is the UNIT_MAX. It ignores nlocktime
[1] and RBF, so it cannot be double spent by you.
[1]
https://en.bitcoin.it/wiki/NLockTime- Jay -
Thanks. But does it also mean that anybody else won't be able to double spend it even if they have the private key?