Ques. I AM PLANNING TO BUY THE APPLE I PHONE 6 PLUS,OR APPLE I PHONE 6,I AM EAGER TO KNOW,WHETHER APPS SUCH AS VIBER ,WHATSAPP,OR IMO,CAN BE DOWNLOADED IN THESE PHONES OR NOT,I AM IN MUMBAI,INDIA.
ALSO,I AM CONFUSED BETWEEN THE LG G3,SAMSUNG NOTE 4,HTC M8,AT THE MOMENT I AM USING BLACKBERRY BOLD 9900 ,AND,AM LOOKING TO UPGRADE,AS MY HANDSET DOESNT SUPPORTS SO MANY LATEST APPS SUCH AS WHATSAPP WITH PHONE,SKYPE ETC.PLEASE ADVICE.
Yes all these apps will work with the phones you listed.
IPhone has less battery and RAM than the Android phones you listed. So you can get only a day's usage (with 3g) out of the phone and then you will have to charge it in the night. While with others you can easily get a day and a half of use. With less RAM you will see tabs reloading in safari If you do multitasking.
As with Android devices we recommend you getting a nexus or Motorola devices as they have the vanilla version of Android installed on them. Others like the note 4, LG etc. put their custom skin over and above the phone's android operating system. This taxes the phone resources more. Even the updates are released first for nexus, Moto devices then after 3-4 months the other phones receive the same update.
And if you want to make a statement more than hardware features you can easily go for the iPhone 6 / 6 Plus.