Please find here some answers
1. Wireless mode..? is it infrared? or somekind of a different one..?
The control is done by the flash of the K10D (or K20D). There are two modes:
- the flash of the K10D only sends a message to the AF540GZ with a small flash light
- the flash of the K10D is fully used to illuminate the subject of the picture and at the same times sends a message to the AF540GZ.
2. Iis it reliable? how far you can put the flash and still trigger it wirelessly..?
I strongly recommend using rechargeable batteries. I have experienced no problem so far.
3. Do creative angles like much higher than the camera or much lower than the camera, trigger it as reliable as horizontal angles?
Yes, everything is possible. The flash is provided with a support and you can play with the orientation from -10° to +90°.
Please have a look at some of my tests here
Pentax K-5 + BG4 + DA* 16-50 + DA* 50-135 + DA* 60-250 + AF-540FGZreivilophotography.weebly.com