1) Tiny Core Linux can be as secure as every other Linux. Basically it always depends on the amount of work you want to put into your own security. Since TCL is a lightweight toolkit base
, we don't provide a "complete totally secure OS with all possible security features", but almost all the tools you need for this (e.g. iptables, virus scanners, tor, anonymizing proxies, etc.) are available through extensions.
2) Your wifi adapter seems to be based on a Realtek device RTL8188CUS and should be supported by the wireless-3.0.21-tinycore.tcz extension (namely the module rtl8192cu).
3) Please rephrase the question, if you really know what you mean
TCL is not providing more or less "wifi security functions" than any other Linux. For the wifi connection itself it mostly depends on the driver of the wifi device and Realtek is not the best supported hardware by Linux in either case.