Test code:

/**
 * Create a new `Ti.UI.TabGroup`.
 */
var tabGroup = Ti.UI.createTabGroup();

/**
 * Add the two created tabs to the tabGroup object.
 */
tabGroup.addTab(createTab("Tab 1", "I am Window 1", "assets/images/tab1.png"));
tabGroup.addTab(createTab("Tab 2", "I am Window 2", "assets/images/tab2.png"));

/**
 * Open the tabGroup
 */
tabGroup.open();

/**
 * Creates a new Tab and configures it.
 *
 * @param  {String} title The title used in the `Ti.UI.Tab` and it's included `Ti.UI.Window`
 * @param  {String} message The title displayed in the `Ti.UI.Label`
 * @return {String} icon The icon used in the `Ti.UI.Tab`
 */
function createTab(title, message, icon) {
    var win = Ti.UI.createWindow({
        title: title,
        backgroundColor: '#fff'
    });

    var label = Ti.UI.createLabel({
        text: message,
        color: "#333",
        font: {
            fontSize: 20
        }
    });

    win.add(label);

    var tab = Ti.UI.createTab({
        title: title,
        icon: icon,
        window: win
    });

    return tab;
}


// added during app creation. this will automatically login to
// ACS for your application and then fire an event (see below)
// when connected or errored. if you do not use ACS in your
// application as a client, you should remove this block
(function(){
var ACS = require('ti.cloud'),
    env = Ti.App.deployType.toLowerCase() === 'production' ? 'production' : 'development',
    username = Ti.App.Properties.getString('acs-username-'+env),
    password = Ti.App.Properties.getString('acs-password-'+env);

// if not configured, just return
if (!env || !username || !password) { return; }
/**
 * Appcelerator Cloud (ACS) Admin User Login Logic
 *
 * fires login.success with the user as argument on success
 * fires login.failed with the result as argument on error
 */
ACS.Users.login({
	login:username,
	password:password,
}, function(result){
	if (env==='development') {
		Ti.API.info('ACS Login Results for environment `'+env+'`:');
		Ti.API.info(result);
	}
	if (result && result.success && result.users && result.users.length){
		Ti.App.fireEvent('login.success',result.users[0],env);
		Ti.API.info("Welcome Rakhi");
		//var phto1=Titanium.Filesystem.resourcesDirectory.getFile('tab1.png');
		var phto1 = Ti.Filesystem.getFile(Ti.Filesystem.applicationDataDirectory,'tab1.png');
			ACS.Objects.create({
			    classname: 'cars',
			    fields: {
			        make: 'nissan',
			        color: 'blue',
			        year: 2005,
			        photo:phto1
			    }
			}, function (e) {
			    if (e.success) {
			        var car = e.cars[0];
			        Ti.API.info('Creation Success:\n' +
			            'id: ' + car.id + '\n' +
			            'make: ' + car.make + '\n' +
			            'color: ' + car.color + '\n' +
			            'year: ' + car.year + '\n' +
			            'photo: ' + car.photo + '\n' +
			            'created_at: ' + car.created_at);

			            var savedcarId= car.id;

			             Ti.API.info('Saved car ID'	+savedcarId);
			            var updatephto = Ti.Filesystem.getFile(Ti.Filesystem.resourcesDirectory,'tab2@3x.png');
			            if(savedcarId){

			            	Ti.API.info('Saved car ID+++'	+savedcarId);


							ACS.Objects.update({
							    classname: 'cars',
							    id: savedcarId,
							    fields: {
							        color: 'purple',
							        mileage: 10000,
							        photo:updatephto
							    }
							}, function (e) {
							    if (e.success) {
							        var car = e.cars[0];
							        Ti.API.info('Update Successful:\n' +
							            'id: ' + car.id + '\n' +
							            'make: ' + car.make + '\n' +
							            'color: ' + car.color + '\n' +
							            'year: ' + car.year + '\n' +
							            'photo: ' + car.photo + '\n' +
							            'mileage: ' + car.mileage + '\n' +
							            'updated_at: ' + car.updated_at);
							    } else {
							        alert('Error:\n' +
							            ((e.error && e.message) || JSON.stringify(e)));
							    }
							});



			            }else{

			            	Ti.API.info('Update falied');
			            }



			    } else {
			        alert('Error:\n' +
			            ((e.error && e.message) || JSON.stringify(e)));
			    }
			});


	} else {
		Ti.App.fireEvent('login.failed',result,env);
	}
});

})();



Console logs:
[INFO] :   I/System.out: ActivityRecorder: before org.appcelerator.titanium.TiActivity@f4fc27a_onCreate(), launchUrl = null
[INFO] :   I/System.out: ActivityRecorder: before org.appcelerator.titanium.TiActivity@f4fc27a_onCreate(), launchUrl = null
[INFO] :   I/System.out: ActivityRecorder: after org.appcelerator.titanium.TiActivity@f4fc27a_onCreate(), launchUrl = null
[INFO] :   I/System.out: ActivityRecorder: after org.appcelerator.titanium.TiActivity@f4fc27a_onCreate(), launchUrl = null
[INFO] :   OpenGLRenderer: Initialized EGL, version 1.4
[WARN] :   EGL_emulation: eglSurfaceAttrib not implemente
[INFO] :   ACS Login Results for environment `development`:
[INFO] :   [object Object]
[INFO] :   Welcome Rakhi
[INFO] :   Creation Success:
[INFO] :   id: 5ac5e1fc04120102212c539a
[INFO] :   make: nissan
[INFO] :   color: blue
[INFO] :   year: 2005
[INFO] :   photo: [object Object]
[INFO] :   created_at: 2018-04-05T08:44:44+0000
[INFO] :   Saved car ID5ac5e1fc04120102212c539a
[INFO] :   Saved car ID+++5ac5e1fc04120102212c539a
[WARN] :   TiBaseFile: (main) [8229,8229] Method is not supported org.appcelerator.titanium.io.TiResourceFile : getParent
[INFO] :   Update Successful:
[INFO] :   id: 5ac5e1fc04120102212c539a
[INFO] :   make: nissan
[INFO] :   color: purple
[INFO] :   year: 2005
[INFO] :   photo: [object Object]
[INFO] :   mileage: 10000
[INFO] :   updated_at: 2018-04-05T08:44:47+0000
[INFO] :   APSAnalyticsService: Analytics Service Started
[INFO] :   APSAnalyticsService: Stopping Analytics Service