both iphone and android receive one phone call

It is not possible to notify both android and iPhone at the same time when you receive a call.

It is possible to receive notifications at the same time among iOS devices, like iPhone and iPad provided that all devices are signed on to iMessage using the same Apple ID.

around the same time. call 1 phone and if that phone does not pick up, then call second phone
android / iphone
or vice versa

What you want is voice call forwarding settings.

Go to Settings -> Applications -> Call -> Additional Settings and you will see call forwarding settings inside.

Your scenario is a typical unanswered call forwarding.

I see settings call to change voicemail for all phone numbers

but not voice call


and not for 1 contact

I see settings call to change voicemail for all phone numbers

but not voice call

and not for 1 contact

It is not possible to do a call forwarding just for 1 contact... it is a general option which applies to all incoming calls.

Voice call forwarding is a basic feature... on what phone to change that settings...

okay for all phone numbers.
how to find settings
android 4.4.2

Android 4.4 KitKat
 
From any Home screen, tap Phone.
While on the Keypad or Logs screen, tap the Menu icon.
Tap Settings.
Tap Call.
Tap Additional settings.
Tap Call forwarding

Source: https://support.t-mobile.com/docs/DOC-10718

It depends on whether your telecom service provider has provided call forwarding to you at no extra cost and if you cannot change the call forwarding option, you need to contact your telecom service provider.

android 5
settings
advanced calling
has to do with video calling

android 4.4.2
no forward
no advanced options
in settings call

android 5
settings
advanced calling
has to do with video calling

android 4.4.2
no forward
no advanced options
in settings call

Which brand and phone models?

first is Samsung galaxy 3
other is Samsung galaxy 5

The GSM code below will work for both Samsung S3 and S5.

*61*[dest]*[sec]#

Whereas [dest] is the detimation tel number for no answer call forwarding and [sec] is the time duration before no answer call forwarding to be activated.

Just dial the above GSM codes in your Phone app.

Source: http://www.geckobeach.com/cellular/secrets/gsmcodes.php

My wild guess is that your Samsung S3 CDMA is either:

Samsung SGH-I535 for Verizon
Samsung SPH-L710 for Sprint

Go to Settings -> about this phone -> device infornation and post back the phone model number.

Besides, what are the telecom service provider? CDMA or GSM?

I use wifi:
Android 5 Samsung-SM-G900V Verizon


This is the only one with cellular service that I can test:
Android 4.4.2 Samsung SPH-L710 for Sprint (Actually Boost mobile)

Besides, what are the telecom service provider? CDMA or GSM?

Do I find this information on the phone, because if I use google, then I am just guessing

:
Android 5 Samsung-SM-G900V Verizon

You need to put a SIM card in your phone in order to receive and place call.

Okay I understand I can not test

Android 5 Samsung-SM-G900V Verizon

You need to put a SIM card in your phone in order to receive and place call.

This is the only one with cellular service that I can test:
Android 4.4.2 Samsung SPH-L710 for Sprint (Actually Boost mobile)
which works without a sim card
There is no sim card slot. There is a memory card slot. but sim card will not fit in a memory card slot.
This phone is made for boost mobile (maybe sprint also: but I have/will not tested on sprint)

You need to port your boost mobile number to sprint which supports conditional call forwarding as boost mobile has removed the said feature and they only offer unconditional call forwarding which is not what you want.

Boost mobile and sprint are CDMA and the GSM code will not work.

The simple way is to port your Boost Mobile number to a prepaid GSM carrier which support conditional call forwarding.

what is difference between conditional and unconditional call forwarding?

second question:
I am sticking with boost mobile
can I do either conditional or unconditional?

Just do a unconditional call forward to your Google Voice number as I see that you have a Google Voice question recently.

thanks for call forwarding with conditions