seem i can turn off and on like normal for the mobile data.
problem is battery saver app cant be use then cant limit the usage an app.
battery drain fast.

contained a lot of bug ...as this is just technical preview

just stick to WP8.1 GDR2 if that is your primary phone

   

now still not working?

Technical Preview is not meant to promote goodness of Windows 10, please please do not get this wrong. At this stage it's solely meant for testing/feedback. Nothing is final expecially UI wise, besides they are not focusing on UI also now.
Yeap correct 
As I've mentioned before doing this will put your phone on waiting to update to Windows 10 TP, with no way of cancelling it or getting any other official updates later. Only way out is hard reset.

Anyway WP8.1 GDR2 is confirmed will be installed as staging update before W10 TP.

Dude, you don't get it, if u do that u won't even get the official Windows 10 update down the road. This is something u need to inform normal ppl before u tell them to update this way, else later they complain what are u going to tell them?

Yes WP8.1 GDR2 is probably the best & most polish one but this is not the official way of getting it. I've seen way too many ppl who jump into W10 TP without realizing the consequences, only to complain so much now. So I always warn ppl now what happens if u choose that way.

By the way, I'm enjoying WP8.1 GDR2 on my Lumia 535, can finally connect BT keyboards to type with that 

Yes it's plain straight forward for us more knowledgeable ppl but not those no idea still wanna try for fun ppl 

This is very important since WP8.1 backup still don't save app data.