The beta ROM is developer version based on Android 4.4. As it's closed beta, it still has many bugs. Please think twice before flashing it.
2. Please back up your data before flashing. Do not restore system data after updating to MIUI 6, otherwise it might cause system unstability.
3. Please update to the latest MIUI V5 verison for Redmi 1S before flashing MIUI 6, and do a full wipe during flashing.
4. Make sure to choose the right device and MIUI Version
Downloads:
Recovery:http://bigota.d.miui.com/5.4.3/miui_HM1SWC_5.4.3_ca2f74366f_4.4.zip
Ota Update for 5.4.2-5.4.3:http://bigota.d.miui.com/5.4.2/miui-ota-armani-5.4.1-5.4.2-a1b3abb39e-4.4.zip
Change log:http://en.miui.com/thread-99362-1-1.html