Functional Analysis Help

Hi everyone! I’m currently learning about FBA's and would really appreciate some advice on the functional analysis from those with experience.

Say you have a young client at school who will often walk/run away when presented with a demand. However, following the behaviour, the client is almost always given access to tangibles and is sometimes observed walking back and forth to the toy box while engaging in the behaviour.

I’m trying to work out how best to differentiate between just escape, just tangible, or synthesised. What type of FA would you recommend in this situation? Would you start with separate test conditions (e.g., escape and tangible) to see whether one function is sufficient (e.g., trial-based), or would straight into a synthesised condition make more sense?

Also, how would you differentiate whether the demand itself is the relevant establishing operation, or whether the client is simply engaging in the behaviour because they want access to a tangible that happens to be available in that context? Or is it both?

Any advice on the most appropriate FA arrangement, or on how you would structure the conditions to tease these possibilities apart, would be really appreciated! I'm still learning, so I might be missing something obvious - please be kind :).