What is the response if master issues normal transaction to secure slave

That's probably more a system design question than an AMBA question.

Typically, I'd expect one of two approaches:

The address is of a TrustZone aware device (e.g. the GIC):  The interconnect routes both S and NS accesses to the device, and allows the device to decide what to do.  What the device does might vary. Using the GIC example again, NS accesses to Secure register/fields behaves as RAZ/WI.  But you'd have to check the spec for the specific device(s).

The address is only ever Secure:  The requester is effectively asking for an address that doesn't exist (remember, strictly Secure and Non-secure are different address spaces).  The interconnect treats it like other accesses to invalid/inaccessible addresses, possibly returning a DECERR.

You might find this guide useful for background reading: Learn the architecture - TrustZone for AArch64 (arm.com)

That's probably more a system design question than an AMBA question.

Typically, I'd expect one of two approaches:

The address is of a TrustZone aware device (e.g. the GIC):  The interconnect routes both S and NS accesses to the device, and allows the device to decide what to do.  What the device does might vary. Using the GIC example again, NS accesses to Secure register/fields behaves as RAZ/WI.  But you'd have to check the spec for the specific device(s).

The address is only ever Secure:  The requester is effectively asking for an address that doesn't exist (remember, strictly Secure and Non-secure are different address spaces).  The interconnect treats it like other accesses to invalid/inaccessible addresses, possibly returning a DECERR.

You might find this guide useful for background reading: Learn the architecture - TrustZone for AArch64 (arm.com)